Ninety-One One Fifty-One, the Fuel Reserve Rule, and the Extra Gas That Keeps You Out of Trouble Holding Over Ripon on the Way Into Oshkosh

Federal Aviation Regulation 91.151 requires that before you begin a VFR flight, you carry enough fuel to reach your first point of intended landing plus a reserve of 30 minutes during the day or 45 minutes at night, flown at normal cruising speed. That’s the legal minimum - but it is a floor, not a plan. Flying into a high-volume arrival like EAA AirVenture Oshkosh, smart pilots plan to cross the initial fix with a full hour of fuel still in the tanks.

What Does FAR 91.151 Actually Require?

In plain language, you cannot begin a flight under visual flight rules unless - considering wind and forecast conditions - you have enough fuel to fly to your first point of intended landing and then keep flying at normal cruising speed for an additional buffer.

During the day, that buffer is 30 minutes. At night, it’s 45 minutes. That reserve sits on top of the fuel it takes to actually get where you’re going.

If you’re flying IFR, a different regulation applies: 91.167 requires a 45-minute reserve after flying to your destination and then to your alternate. But most airplanes streaming into Oshkosh are VFR, and that’s where the trouble tends to show up.

Why the Legal Minimum Isn’t a Real Plan

The regulation tells you the absolute least you can carry and still be legal. It does not tell you what a prepared pilot does. Those are two very different numbers, and the gap between them is exactly where you want to operate.

Treat the 30-minute reserve as a floor, not a target. Running a tank dry is almost never a mechanical failure - it’s a planning failure, and it happens to experienced pilots, not just students. Pride and get-there-itis put more airplanes in the corn than bad weather does.

How Much Fuel Do I Need to Fly Into Oshkosh?

Here’s a scenario that plays out every July. You depart southern Illinois on a well-planned cross country. On paper it’s 1 hour and 45 minutes to Oshkosh, and your tanks hold 4 hours. More than double what you need - you feel golden.

You’d be right, if Oshkosh were a normal airport on a normal day. It isn’t.

During AirVenture, Wittman Regional Airport runs under a special air traffic procedure published in the annual AirVenture NOTAM (Notice to Air Missions). You fly to the town of Ripon, Wisconsin, follow the railroad tracks northeast to Fisk, and controllers stationed there identify your airplane by color and ask you to rock your wings to confirm you heard them. The whole line moves at roughly 90 knots and 1,800 feet, wing to wing, half a mile in trail.

When volume spikes, controllers do something completely reasonable: they hold you. Sometimes you circle a lake. Sometimes you’re sent back around. Sometimes the arrival closes entirely because the field is saturated.

So that 1:45 flight can become 2:30 once you spend another 45 minutes circling - low, slow, and surrounded by more airplanes than you’ve ever seen. That comfortable buffer evaporates in real time. It’s the worst possible moment to discover you’re tight on gas, and the “you’re so close” voice starts drowning out the “divert now” voice.

How Should I Build My Fuel Plan for the Fisk Arrival?

The AirVenture NOTAM itself tells you to arrive with ample fuel and a plan to divert. That’s not caution for its own sake - it’s the people who watch this arrival every year telling you what they’ve seen.

Here’s how to do it:

1. Throw out the 30-minute reserve as a planning number. For Oshkosh this week, plan to have a full hour of fuel in the tanks when you cross Ripon - not at the destination, but before you even enter the arrival. Everything after Ripon is unpredictable. An hour gives you room to hold, room to think, and room to peel off without your heart rate changing.

2. Know your divert fields cold. Fond du Lac, just to the south, runs its own arrival procedure during the show specifically to catch airplanes that need to divert. Ripon, Waupun, and other nearby fields are options too. Write down the frequencies before you launch.

3. Set a hard divert number on the ground. Decide the exact fuel state at which you say, “That’s it, I’m going to Fond du Lac.” That decision is a thousand times easier to make the night before than to invent at 1,800 feet in a conga line.

What Trips Pilots Up About the Fuel Reserve Rule?

Three misunderstandings come up again and again.

Normal cruising speed means the speed you actually fly. Not best economy, not an optimistic number from the back of the manual. If you plan your reserve at a fuel burn you never actually see, your reserve is a fantasy.

“Forecast” conditions include the wind. A headwind you didn’t plan for eats your reserve. If the winds aloft are stiff, your plan has to account for the extra time - and therefore extra fuel - which means less cushion when you reach the hold.

Don’t trust your fuel gauges. Certification only requires the gauge to read accurately when the tank is empty - exactly when the information is useless. Manage fuel with a watch and a known burn rate instead. If you took off with 50 gallons, you burn 10 gallons an hour, and you’ve flown 2 hours, you have 30 gallons - no matter what the needle says. Time and burn rate are the truth; the gauge is a cross-check.

What Does the Examiner Want on the Checkride?

The Airman Certification Standards (ACS) expect you to know these fuel requirements cold. In the oral, state the day and night VFR reserves without fishing for them: 30 minutes and 45 minutes.

But the examiner is really looking for judgment. They want to hear you describe the legal minimum as a floor, explain what you’d actually plan, and connect the regulation to a real decision. That connection is the whole point of learning it.

Key Takeaways

• FAR 91.151 requires a VFR fuel reserve of 30 minutes by day and 45 minutes at night, at normal cruising speed - a legal floor, not a plan.
• For Oshkosh, plan to cross Ripon with a full hour of fuel because holds, go-arounds, and arrival closures can add 45 minutes or more of unplanned flying.
• Plan your burn at the speed you actually fly and account for forecast headwinds.
• Trust your watch and known burn rate over your fuel gauges, which are only certified accurate at empty.
• Decide your divert number on the ground, and know Fond du Lac and other nearby fields cold before you launch.