Hi, hope you excuse me reviving an old thread instead of creating a new one. I am searching for the registration of two flights I took back in December 2015 (same airplane on both flights):

2015-12-08 DL5719 YVR SEA 09:54 10:55 E170
2015-12-08 DL5750 SEA SJC 11:40 13:55 E170

The BTS search was no help, neither the departure search from SEA nor the arrival search for SEA or SJC provided any result (when searching for Delta). I was wondering if maybe the DL flight was a codeshare (I do not remember if this is the case). When looking at the current schedule (flight is now called DL5751 for SEA-SJC), it shows me Compass Airlines as the operating airline: https://www.flightaware.com/live/flight/DAL5751

My question to you: where else can I look for the registration or how can I find out the operating airline of the flight back then?

Thanks in advance and regards from Paris