I have used phenergan successfully on many long haul flights with my three children. (we live in new zealand and have flown to UK several times) I was advised by the pharmacist to give the full dose to ensure it works properly, otherwise it can have the reverse effect. Also I wait until they have eaten a meal and the cabin lights are being turned off - on a night flight. I have also used it occasionally to help with jet lag at the destination ie . when they wake up at 3am ready to start the day!! As they have grown older I don't need to use it. However by far the best bet is to fly with an airline with a decent entertainment system!