33k views

### What determines the maximum altitude a plane can reach?

What factors determine the maximum altitude for a plane? Is it limited by wing design, engine thrust, and so on? Is there a formula by which one can calculate the maximum altitude a plane can reach?
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### Why are many jet aircraft designed to cruise around FL350-370?

If the flight distance permits, the B737-800 will cruise at FL350, the A320 a little bit higher... Flying at FL370. Photo: Live from the Flight Deck by GolfCharlie232 (reframed) Elements such as ...
30k views

### Why can't jet engines operate with supersonic air and how do they slow it down?

Typically jets cannot operate when intake airflow is supersonic relative to the engine. Why is this so? Also, why are scramjets able to use supersonic air? To slow down the air to subsonic speeds, ...
2k views

### Why does the U-2 Dragon Lady not have swept wings?

Swept wings increase the critical mach number for aircraft with otherwise identical wings (Source 1). The U-2 Dragon Lady is limited in altitude by its critical mach number, as it needs more speed in ...
7k views

### Why do some military aircraft use variable-sweep wings?

There are a couple of American military aircraft (the retired F-14 and the B-1 come to mind immediately), that have variable swept wings. I know that they keep the wings full out (roughly ...
6k views

### What are the merits of an inlet cone/spike/centerbody vs. a 2D inlet?

And which is better for a scramjet? Is a 2D inlet basically a "2D cone"? Similar to how an aerospike engine is made "2D" in the linear aerospike? What's inside the cone/spike? Or is it just hollow?
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### why are regional cruising altitudes higher than those of international much longer flights?

How come, for example, the average cruising altitude of let's say the Westjet Boeing 737-600 from CYWG to CYVR flies at an altitude of 38,000 feet-40,000 feet, yet the Air Transat Airbus 330-200 ...
5k views

### Why are there no Mach 4+ fighter planes?

Why are there no Mach 4+ fighter aircraft? It seems that such aircraft would have massive advantages when it comes to being able to fire longer range missiles and evade return fire.
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### Which supersonic airplanes use Pitot Air intakes?

Which supersonic (fighter) airplanes use the simple Pitot Air Intakes / Normal Shock Inlets? Two examples already seen here on Aviation.SE (one and two) are Dassasult Rafale ($Ma \leq 1.8$) Image ...
2k views

### Is there a limit to the possible altitude for electric jets?

So I was thinking about Elon Musk's supersonic electric jet idea. Assuming we have sufficiently energy-dense batteries, where would the limits be in terms of speed and altitude. His logic seems to ...