You don't need a printed ticket or itinerary as "proof". If you check in online you can print your boarding pass or get it printed for you at the airport. Or just turn up at the airport and present your passport to be scanned at check in, this will retrieve your booking and enable your boarding pass to be printed.
How do you get your flight ticket when you book online?
Airline and travel agency sites will walk you through the purchase process, and it's super easy to follow. After you've selected your flight online, you'll be prompted to pay with a credit or debit card. The screen will then present you with your payment confirmation receipt, your eTicket, and your itinerary.2018-11-12
How do I get my plane ticket if I bought it online Expedia?
If you check in online you can print your boarding pass or get it printed for you at the airport. Or just turn up at the airport and present your passport to be scanned at check in, this will retrieve your booking and enable your boarding pass to be printed. You can often do this at a self service kiosk. 4.