aircraft

[doncaster]

why do aircraft need head wind to take off safely?

[KebabMeister]

To increase lift at lower speed.

[Clanad]

But, the aircraft doesn't need head wind to take-off safely.  The head wind merely shortens the take-off roll, but the aircraft is required to meet runway requirements as to length without head-wind consideration.  Actually, to make much difference anyway, the wind would have to be in excess of 20 to 25 knots...

[Cathyhuns]

Planes need to LAND into the wind to ensure that they can stop before the end of the runway.  At single runway airports it would be dangerous to have planes taking off and landing in opposite directions so therefore planes take off into the wind too.

[Clanad]

Again, aircraft do land into the wind, but they are assured of a safe landing as to distance by other factors than the wind.  In fact, all large aircraft are allowed to land with a maximum of 10 knots tail wind... All aircraft operators have charts defining landing and take-off distances for all airports served.  The distance variations are dependent, primarily, on the weight of the aircraft, the air temperature and the slope, if any, of the runway.  Additionally, the stopping distance of aircraft is not dependent on the thrust reversers.  The required landing distance is based on dynamic braking only.  The use of the thrust reversers only enhances the safety already inherent...