To take advantage of the best prices you will need to prove you are a leisure traveller, on the way to the airport, so you will need to provide either your flight numbers or yr holiday booking reference. I don't think you will need to give this when you arrive at the station but you may be asked to provide them on your travels from norwich station to luton airport.
Going to the airport on the train is great, you can take a nap, read (even at night), play a game, or just gaze out of the window... The other restriction to buying these inexpensive tickets from the station to luton airport is that there must be at least two grown ups travelling together. But another great benefit is that children go free. All children under five go free, and then one child over five but under sixteen per adult travelling on the train to luton airport.
make sure you leave plenty of time to get to the airport early enough to eat, shop and so on, so check the times of trains from the station before you go. If you have time to kill at the airport you can always read a book or play travel scrabble again! As you have bought your train ticket in advance, you don't need to worry about the opening hours of the station.
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