What a fuel stop actually saves
Every pilot who manages an airplane has done this math on a napkin: the FBO at the destination wants $9.40 for Jet A, the field twenty miles back wants $7.10, and the tanks need 150 gallons. Is the stop worth it? Here is the math JetDesk runs, and the two places where napkins usually go wrong.
01The gap is not the savings
The headline number is easy: a $2.30 gap on 150 gallons is $345. That is the gross. The stop itself costs fuel, and the fuel it costs is bought at the cheap field, so the real question is how many gallons the extra takeoff, climb, descent and detour burn, and what those gallons cost.
For a Meridian-class turboprop, a stop cycle (taxi, takeoff, climb back to a cruise you already had, and a second approach) runs about 15 gallons. A ten-minute detour at 40 gallons an hour is another 7. Twenty-two gallons at $7.10 is $156. So the stop nets about $189 before fees, not $345. Still worth it, but by half as much as the napkin says.
02Fees turn good stops into bad ones
A $75 ramp fee waived with a fuel purchase is fine. A $150 landing fee that is not waived is most of your margin. JetDesk counts the fee against the stop as a flat line item, and shows the break-even gap: the price difference at which the stop exactly pays for itself. For the numbers above the break-even is about $1.03 a gallon. Below that gap, tanker on.
03Time is the number nobody writes down
A stop adds the detour plus ground time. Twenty five minutes on the ground is optimistic at a busy FBO; forty is normal. If the owner is on the airplane, a 35 minute stop to save $190 is a conversation, not a decision. JetDesk shows the time added next to the dollars so that conversation happens before the flight, not on the ramp.
04Where the prices come from
No public API publishes FBO fuel prices, and the sites that list them do not allow scraping. JetDesk uses the prices you and your crew log, flags them stale after two weeks, and shows the market reference (EIA jet fuel spot and crude) so you know when the whole board has moved since you last checked. Ten seconds per airport to log a price keeps the whole crew's math honest.
05Try it on your own route
The Fuel Stop tab runs this calculation with your airplane's burn, and the route finder ranks every Jet A field within a corridor of your route by net savings. Free accounts get the calculator; the route finder is part of Pro.
More field notes
Reserve fuel, and the alternate nobody plans
How JetDesk decides whether a leg makes reserve, and why the alternate is where most fuel stops really come from.
Why block time swings twenty minutes
How the FAA winds aloft forecast becomes a groundspeed for each leg, and why the return leg costs more than the outbound one.
Weight before fuel: payload runs out first
Zero fuel weight, max fuel by weight and landing weight for a Piper Meridian with five aboard, and how JetDesk shows it per leg.