Originally Posted by Jennifer
Doc said "if I live to be 100, which I almost have" in It's About Time.
He also said Jules and Verne are going to college, which would mean that 19 years had passed since their conception. That would make Doc 90. Add in the amount of time it took Doc and Clara to be married, and the time it took to conceive a child, and the time definitely lines up with Doc's statement that he's almost 100.
The DeLorean had the ability to time travel before the crash because the time ripple didn't catch up to it yet since Doc didn't fade from existence until after they traveled through time.
As for the flying parts, they still exist in the timeline in 2015 (and as I mentioned before the future already exists as evidenced by Marty and Jennifer living in the future despite the fact that they hadn't lived it yet), since Doc Brown wasn't the one who invented them. Since they still exist, the time ripple took longer to catch up to it, as it had with Marty and the DeLorean itself.
good point. Doc does state in the first episode he visited Marty and Jennifer in 2011 so the future does exist (as we also see at the end of the game)
the critical junction point of the FCB timeline is Emmett avoiding seeing Frankenstein. He avoids it at basically the exact same time Doc and Marty go back to the future. I don't know why people find it so inconceivable that Doc wont live as long without his rejuvenation.