Definition: In this task, you need to generate an appropriate title for the given summary of some paragraph. The generated title must be short and should include the main topic of the given text. Your summary should be less than 20 words long.
Input: Air passenger duty is a tax on passenger flights from UK airports. It was first introduced in 1994 and was mainly designed to raise money, rather than for environmental reasons. But it has also been seen by some as having potential environmental benefits by discouraging people from taking certain flights.

Flybe: What is air passenger duty?