I read somewhere in the forums claim that everyone who wasn't flying either Airbus A320 series, Boeing 737 NG or Bombardier CS series would go bankrupt in MT7.
Well, I proved you wrong!
I had the following aircraft when MT7 ended:
325 x MD-90
101 x A330/A340
80 x E-jets
Average active fleet age = 15,6 years.
And my finances were good too. I was making $140,000,000 a week in pure profit for the last couple of game years. I'm not sure how high the fuel price was in the end, but in my opinion this means you don't need the absolute most fuel efficient aircraft to succeed. My fleet was the 17th biggest in the game world, but my fuel usage was the 12th biggest. I was not flying very fuel efficient aircraft. 373 aircraft were owned, 133 were leased. But even my old leased A340 planes were making money. If fuel prices had increased another 30% I would have survived, but with lower profits. 50% and I would have lost money.