PILOT YOUR RETIREMENT FLIGHT TO YOUR TARGET AGE
How Crashline Works: If market drops or high spending push your net worth below $0, you enter the CRASHLINE ZONE. You get a 10-Year Grace Period to climb back. Below zero nothing is invested and the shortfall is borrowed at 5% a year, so only income above your spending (part-time work, the pension from 62) or the one-time downsizing lifts you out — spending cuts only slow the fall. Stay in the crashline for 10 consecutive years and your flight is destroyed!
PILOT & FUEL PARAMETERS Pre-Flight Deck
Every completed flight is posted to the global leaderboard under this callsign, where other pilots can see it.
50-year horizon (age 50 to 100). Start 18–90; the target must be at least 10 years later, up to 100.
Automatically shifts from growth stocks to conservative bonds as your age increases, year by year during the flight.
Historical sequences play the real years once, in order (S&P 500 total return, 10-year Treasuries, T-bills and CPI); the rest of the flight continues with simulated returns.
Setup is locked while a flight is in the air or paused, so the flight is scored on what it launched with. Tactics stay available; reset to change the setup.
MID-FLIGHT COCKPIT ADJUSTMENTS (6 TACTICS)
Switch on before launch or during the flightPart-Time Income
Earn $15,000/yr (today’s money, rising with inflation). Income above your spending is added to the portfolio.
Cut Spending 15%
Trim living expenses by 15% for every year it is on.
Cash Bucket Shield
After a year in which stocks fell, withdrawals come from cash, then bonds, instead of selling stocks, and rebalancing waits. Needs a cash allocation above 0%.
Dynamic Guardrails
Guardrail rule: cuts spending 10% in any year the portfolio starts more than 15% below its peak.
Downsize Real Estate
One-time home sale: +$100,000 (today’s money), once per flight. Chosen before launch it lands in year one; it cannot be undone.
Social Security Benefit
Claim +$20,000/yr (today’s money, inflation-linked) from age 62.
GLOBAL RETIREMENT FLIGHT LEADERBOARD
Every flight flown by every pilot, on one shared board — filter it by scenario. Flight score rewards reaching the target age, the fewest crashline years and the biggest ending nest egg.
| Rank | Pilot Callsign | Scenario Preset Category | Reached target age? | Crashline Years | Tactics Used (Penalty) | Ending Nest Egg | Flight Score |
|---|
Amounts are shown in the currency of the page each flight was flown on ($ English, € Spanish, R$ Portuguese) and are not converted.
1,000 MONTE CARLO STRESS-TEST ENGINE
Simulates 1,000 randomized retirements from age 50 to 100 (50 years) with the same yearly rules as the cockpit flight: your allocation, target-date fund, market sequence and switched-on tactics.
Paths reaching the target age with money left.
50th percentile nest egg at the target age.
10th percentile stress test outcome.
90th percentile top tier growth.
Percentile Wealth Distribution Over Time
| Retirement Age | 10th Percentile (Worst Case) | 25th Percentile | 50th Percentile (Median) | 75th Percentile | 90th Percentile (Best Case) |
|---|---|---|---|---|---|
| Click "Run 1,000 Simulations" to generate Monte Carlo trajectory data. | |||||
Success rate by withdrawal rate
The same plan at every initial withdrawal rate from 2% to 7%, in quarter-point steps, with 500 runs per rate. The highlighted point is the highest rate that still succeeds at least 90% of the time.
Run the simulations to draw the curve.
FIRE FLIGHT ACADEMY: CORE RETIREMENT LESSONS
Master the financial science of wealth decumulation, asset allocation balancing, and longevity protection.
The 4% Safe Withdrawal Rate Rule
Derived from the landmark 1998 Trinity Study, the 4% rule states that withdrawing 4% of your initial portfolio in year one (adjusted for inflation each subsequent year) historically provided a 95%+ success rate over 30-year retirement periods.
Sequence of Returns Risk (SORR)
Market timing matters tremendously once you enter decumulation! A severe stock market crash in the first 5 years of retirement forces you to sell stocks at bottom-barrel prices, sending your flight into the crashline zone.
Target Date Funds & De-Risking Glidepaths
As retirement progresses, holding 100% aggressive equities increases crash exposure. Target Date Funds automatically shift asset allocation toward fixed income (bonds/cash) over time to lock in gains and buffer volatility.
Dynamic Spending Guardrails & Part-Time Work
Flexible retirees don't rigidly withdraw fixed amounts during severe bear markets. Taking a part-time job, cutting spending by 15%, or tapping cash buckets lets your stock portfolio recover without forcing liquidations.
What a Monte Carlo simulation tells you
Every other retirement calculator gives you one number, produced by assuming the market returns the same amount every year. It never does. This simulator runs your plan a thousand times over, drawing a different sequence of market years each time, and reports not a number but a probability: the share of those thousand lives in which your money outlasted you.
How the thousand runs work
For each of the 1,000 runs and each year within it, the simulator draws a random return for stocks, bonds and cash, and a random rate of inflation, each from a normal distribution with the arithmetic mean and standard deviation of the US record from 1928 to 2025 (Aswath Damodaran’s historical returns data): stocks (S&P 500 with dividends) 11.9% a year with a standard deviation of 19.4%, 10-year Treasuries 4.8% with 7.9%, Treasury bills 3.4% with 3.0%, and inflation 3.1% with 3.9%. At the start of each year that year’s withdrawal comes out at that year’s prices; the portfolio, rebalanced to your allocation, then earns the weighted return, and prices rise by the year’s inflation — so every later withdrawal is larger by all the inflation since you retired. The cockpit flight uses exactly the same yearly rules, one path at a time.
The thousand results are then sorted, and three of them are shown: the 10th percentile, the median and the 90th. The median is the ordinary outcome. The 10th percentile is the one that matters — it is what happens when the draws go against you, and a plan that only works at the median is a plan that fails one time in two. A run succeeds if it reaches the target age with money left. Below zero nothing is invested and the shortfall is carried as debt at 5% a year; a run that stays below zero for ten consecutive years is ended there and counted as ruined.
What it assumes
- Returns are drawn independently each year from a normal distribution. Real markets have fat tails — extreme years happen more often than a bell curve predicts — and they cluster, so a bad year is more likely to be followed by another. A real stretch such as 1966–1981 can therefore be worse than almost any simulated path; the historical sequences in the cockpit replay it.
- Asset classes are drawn independently of each other. In a real crisis correlations rise towards one, which is precisely when diversification is supposed to help.
- Your withdrawal rises with inflation regardless of what the portfolio did, unless you switch on the spending-cut or guardrail tactics. Real retirees spend less after a bad year, which is the single most effective defense available — and in this model it is only there if you choose it.
- No taxes and no fund fees. Part-time income, a pension and downsizing are only included when you switch those tactics on, in today’s money and rising with inflation. Each of those shifts the result, and not all of them in the same direction.
Read the success rate as a comparison tool, not as a forecast. Ninety percent here does not mean a nine-in-ten chance in the world; it means this plan failed a tenth of the time under these assumptions, and you can see exactly which change makes that number move.
A worked example
A portfolio of 800,000 held 70% in stocks and 30% in bonds, drawn down at 4% a year — 32,000, rising with inflation — over thirty years, succeeds in about nine runs out of ten: 91% across 40,000 simulations, in the same range the Trinity Study found in US history. The median run ends with around 3.7 million in future money, roughly 1.5 million in today’s money — almost twice the starting balance after inflation — which is the counter-intuitive part: the typical outcome of a sustainable withdrawal plan is dying rich. The 10th-percentile run, by contrast, ends with only a few tens of thousands left.
Now raise the withdrawal rate to 5%, or 40,000 a year. The median still ends with more than it started with after inflation — but the success rate falls to about three in four, and the 10th-percentile run is out of money roughly twenty-two years in. One percentage point of withdrawal costs about fourteen points of success, and the damage is all in the tail a single average never shows. Choose the 1966–1981 sequence and even the 4% plan almost never lasts: independent draws rarely produce a stretch that bad, which is what the historical sequences are there to show. To reproduce these runs, set the nest egg to 800,000, spending to 32,000 or 40,000, the allocation to 70/30/0 and the ages to 65 and 95, then open the 1,000 sims tab.
How the flight score works
A flight that reaches its target age with money left earns a base of up to 5,000 points, in proportion to the years flown against a 50-year reference retirement: a 30-year flight earns 3,000, a flight of 50 years or more 5,000, and no flight earns less than the 1,000 a flight that fell short gets. The board then adds a bonus for the harder presets (Tight Lean FIRE 2,000, High Risk SWR 1,500, custom 1,000, Trinity 800, Fat FIRE 200), takes away 500 points for every year below zero and 75 for every year each tactic was switched on, and adds one point for every 2,500 of ending balance. The total is held between 100 and 100,000, and the debrief shows each line before the score is posted.
The board is decided at launch, not at landing: a flight counts as a preset only if it was flown on that preset’s nest egg, spending, ages and allocation, against the simulated market and without the target-date fund — anything else is a custom scenario. The setup is locked for the length of the flight, and downsizing can be used once per flight.
Common questions
- Why a thousand runs and not more?
- A thousand is enough for the success rate to be stable to within a couple of percentage points, and few enough to finish instantly in your browser. Running ten thousand would narrow that to under a point without changing the decision.
- Why does the result change each time I run it?
- Because the draws are random. A success rate that swings by a point or two between runs is normal; one that swings by ten is telling you the plan is sitting on a knife edge, which is itself the answer.
- What success rate should I aim for?
- There is no correct threshold, and chasing 100% usually means working years longer for protection against scenarios in which you would have cut your spending anyway. What matters more is knowing which lever — spending, allocation, or one more year of saving — moves your number the most.