Do planes fly at maximum speed? This is a question that many travelers have asked themselves. While it may seem like a simple yes or no question, there’s a little more to it.
We’ll discuss six reasons why planes don’t fly at their maximum speed below.
- Cruising speed is more efficient
- Maximum speed puts too much strain on the plane’s structure; it’s unsafe
- The main benefit outweighs the cost. Max speed would cost the airline significantly more than the benefit they get from reducing the duration of the flight
- Airfare rates would skyrocket
- Drag increases exponentially as planes approach Mach 1, which cripples fuel-efficiency
- Planes need to follow what’s called a “cost index” to remain the most efficient
6 Reasons Why Planes Do Not Fly at Maximum Speed
In general, commercial planes do not fly at their maximum speed. They are designed to cruise at a speed of about 500-550 miles per hour. The max speed of most commercial aircraft is only slightly higher at about 600 to 650 mph.
Commercial planes do not fly at maximum speed to save money on fuel and stay in great condition. If planes flew at max speed all the time, they’re risking serious damage to the engines and structure. Airlines definitely want to avoid buying a new passenger plane or jet, if possible.
At cruising speed, planes fly at about 35,000 feet. The higher planes fly, the thinner the air. Therefore, the faster they can fly. So planes fly high to reach their cruising speed. They can afford to fly for a long time without losing a lot of money because of the thinner air.
The thicker the air, the more wind resistance. So if a plane doesn’t reach cruising altitude, its fuel efficiency will decrease.
Most commercial planes aim for what’s called long-range cruise speed, or LRC. It’s defined in the context of maximum range cruise speed, or MRC.
MRC is the speed that a plane should go that is the most fuel-efficient. LRC is the speed above MRC that results in a 1% decrease in fuel mileage. This 1% decrease results in a 3-5% speed increase, which is a good payoff.
Even though airlines are paying a little more, the time they save getting to their destination makes the 1% decrease worth it.
What’s the exact speed you can get the 1% decrease in fuel efficiency? Well, it depends on the aircraft and requires some complex calculations done by mathematicians.
What we do know, though, is that at a plane’s cruising speed, it flies most efficiently. This means that the plane can stay in the air for longer. It can also carry more passengers and stay fuel-efficient.
Depending on the aircraft, a plane’s cruising speed can be anywhere from 500 to about 650 miles per hour (about Mach .65 to Mach .85.
For example, the Boeing 787 Dreamliner, a commercial jet, flies at about 650 miles per hour. Its top speed is around 700 mph, which is not that much faster. In fact, it’s not even 10% faster.
So, flying the plane at max speed would not significantly decrease the duration of the flight relative to the cost the airline will have to pay for using the extra fuel.
Also, if planes flew at their max speed all the time, airfare rates would skyrocket.
Airlines would have to pay thousands of dollars more per flight to get people to their destination. Sure, it may be faster, but not fast enough. You probably don’t want to pay twice as much to save 20 to 30 minutes on a flight. Airplane tickets are already expensive as it is!
As you increase speed toward Mach 1, (about 767 miles per hour – the speed of sound), drag increases exponentially. This drastically reduces fuel efficiency. Not only that, but the wings may tear apart.
In contrast to planes, most commercial jets fly a little faster, around 575 mph to 650 mph.
Pilots use what’s called a cost index to determine take-off speed, cruising speed, and landing speed. Mathematicians use a complex formula to determine these numbers and air traffic control communicates it to the pilots while they’re on the plane.
Cost index describes when you should fly slow to save money on fuel, or when you can afford to fly faster. This costs more but you will get to the destination faster.
A low cost index means that it’s most fuel-efficient to slow down. A high cost index means increasing the plane’s speed is worth it, based on the amount of time that you’ll save.
Typically, if planes are delayed, which costs a lot of money, the cost index increases. This is because it’s more cost-efficient to get to the destination faster.
Cost index is calculated by taking time costs per hour and dividing them by fuel costs per hour.
Time cost includes the following:
- Maintenance ($ per hour)
- Cost of engines and auxiliary power units (APUs)
- Flight crew cost ($ per hour)
Each time a plane flies, it gets a little more worn down or depreciates. This means that the value of the plane depreciates, too. So, in other words, airlines lose a little bit of money every time a plane hits the skies.
Think of the last time you bought a car. If you bought it for $25,000 and try to sell it eight years later, the value will depreciate. You might be able to sell it for 8-10 grand, maybe less. The exact price will depend on how many miles you drove it and any repairs it has needed.
So, by accounting for depreciation in this time cost variable, airlines are trying to compensate for that lost money.
Fuel cost is simply the amount of money that fuel costs per hour. This cost can be expressed in pounds/hour, kilograms/hour, or sometimes cost per 100 pounds of fuel used. This can vary widely depending on the airport.
In some of today’s planes, all the pilot has to do is type in the cost index on their controls and it calculates the cruising speed, takeoff speed, and landing speed.
Pilots can’t just fly the plane at any speed they’d like. For one, it’s dangerous, and second, it costs the airline a lot of money. So if they wanted to increase speed for a short period of time, they probably would have to ask the dispatcher for permission.
This can be practical in real-time. For example, if a pilot finds that they have a lot of fuel left and only a short distance left to go, they could increase the speed. Especially on planes with fewer passengers, this is a real possibility.
Why? Well, the more passengers on the plane, the heavier it is. And the heavier the plane, the more fuel it takes to move it.
In contrast, the fewer passengers on the plane, the lower the cost of fuel will be if you speed up.
That wraps up our article ‘Do planes fly at maximum speed?’
In short, max speed is so close to cruising speed that it’s not worth it for airlines to spend the extra money to get passengers to their destination.
The cruising altitude of commercial jets and planes is the optimal range for fuel efficiency. Any higher and the drag increases dramatically – too much to justify flying at that speed. As most commercial planes approach Mach 1, it becomes increasingly unsafe to pilot them, and the wings may tear apart.
To learn more about aircraft, check out the articles below!