Rule 5b. Never use single quotation marks in sentences like the previous three. Incorrect: I had a visit from my 'friend' the tax man. The single quotation marks in the above sentence are intended to send a message to the reader that friend is being used in a special way: in this case, sarcastically. Avoid this invalid usage.
Why do jets leave a white trail in the sky? Jets leave white trails, or contrails, in their wakes for the same reason you can sometimes see your breath. The hot, humid exhaust from jet engines mixes with the atmosphere, which at high altitude is of much lower vapor pressure and temperature than the exhaust gas.
The afterburner is an easy way to add power for short bursts, such as take-off or in a dog fight. But the afterburner consumes a lot of fuel. Fighter jets use the afterburner to fly faster than the speed of sound for long periods, but it decreases the range they can fly without refueling. The F/A-22 is the first American fighter aircraft with the ability to supercruise, or fly at supersonic speeds without using the afterburner. In early flight tests, it sustained speeds of Mach 1.5 -- that's one and a half times the speed of sound -- without using the afterburner.