Travel plan or flight ticket
Your travel plan / flight ticket is often e-mailed to the address you provided when you booked your ticket. You should be able to find it in your inbox, unless you have deleted the e-mail. Try searching for the airline's name in your inbox or in your trash folder. If you still cannot find the travelplan, you can login on the airline's website and download it again or you can contact customer support and ask for a copy.
Boarding pass
Some airlines and courts require a copy of your boarding pass to process your claim. If you have lost your boarding pass, and you are no longer able to download it when logging in on the airline's website, you can contact the airline or the travel agency from which you bought your ticket and ask for a 'Boarding Certificate'. A Boarding Certificate is equivalent to a boarding pass and can be used to process your claim.