Originally Posted by
LondonElite
Buy yourself a garment bag and get changed in the airport on arrival if you have to. Or wear your suit on the plane. Don't show up to an interview with a backpack unless you are looking to get a job as a camp counsellor. And don't over-think this.
OP is going to a hotel for the night from the airport. The interview is the following day. It would be pointless to change at the airport so as to wear the interview suit to arrive at the hotel.
Whether a professional looking backpack is acceptable depends on the OP's field and level. It's not a universal no-no IMO. Many interviewers would understand a non-business student bring a backpack to interview for an entry-level position. In other areas, such as computer science, most research, and academia, a backpack would not even be noticed.