35. (1986) You need to fly from Leningrad to Seattle next week. Thankfully, you’ve found a great itinerary involving two nonstop flights with a single connection. Best of all, you’ll be on the same airline all the way through. Identify the airline, the routing and the two different aircraft types involved.

Per joejones: I think #35 is probably a European carrier, maybe BA via LHR on a combo of 757-200 and 747-200. Aeroflot's SEA services came after the fall of the USSR iirc, and I think they were using Western equipment at that point...

Per WHBM: I'll go for a flight from what is virtually and commercially a suburb of Leningrad (St Petersburg) nowadays, with a Finnair DC9-10 for the short hop to Helsinki, followed by a Finnair DC-10-30 from Helsinki to Seattle. I think their flights to there used to continue to LAX.

And the winner is..... WHBM! I don't feel like nitpicking this afternoon so I'll let it slide that the DC-9 variant employed on the LED-HEL route was the larger -50. Here's the itinerary -

Finnair AY 713 Leningrad (LED) 435p-430p Helsinki (HEL) DC-9-50 Su
Finnair AY 143 Helsinki (HEL) 705p-640p Seattle (SEA) DC-10-30 Su