Ask the Captain: Did planes fly faster in the past?

Question: Are planes flying slower these days because of the price of fuel?

-- submitted by reader Steve, Mt. Zion, Ga.

Answer: Airplanes are flying more efficiently which, in some cases, is slower. However, one of the most fuel efficient speeds, known as long-range cruise, is not being used very often.

The operators are balancing speed vs. economy, using the flight management computers to pick the best speed. When there is a tailwind, it makes sense to fly slower to get the extra fuel economy while still arriving on time. When flying into a headwind, usually they increase speed to minimize the time in the wind and still arrive on time.

The price of fuel is a big part of the decision, but not the only one.

Q: How many of gallons of fuel are used per hour of flight? Can you break down how much is burned during takeoff and at cruising altitude?

-- Jon, Gilbert, Ariz.

A: Different airplanes burn different amounts of fuel. The weight of the airplane has an effect on fuel burn, so does altitude and temperature. With so many variables I am unable to answer directly, but here are some representative figures:

A 737 or A320 will burn approximately 5,000 pounds or 740 gallons per hour in cruise flight.

During a takeoff run, the burn could be 20,000 pounds or 3000 gallons per hour.

A 747-400 will burn approximately 24,000 pounds or 3,500 gallons per hour (this an average figure that can vary significantly) in cruise.

As you can see, the fuel burns vary considerably.

Q: It appears to me that flying is no faster than the 1950s when the 707 was introduced. If so, why are we stuck well below Mach 1?

-- Richard, San Angelo, Texas

A: The price to get above the speed of sound has so far proven not commercially viable. You are right, we are flying about the same speed we did in the early jets of the fifties.

Concorde proved that we can build a supersonic airliner. The price for a ticket was high but the experience was wonderful. Hopefully we will build another supersonic airliner in the near future.

John Cox is a retired airline captain with U.S. Airways and runs his own aviation safety consulting company, Safety Operating Systems.