One idea that is really stuff of science fiction is using gravity to create an bubble around your plane or spaceship to exclude it from the external forces effecting it. Because the craft experiences no external forces during flight, it will obtain absolute Zero G while in any type of atmosphere or no atmosphere it is in at the time. This will allow for sharp turns and speeds not previously obtainable by modern methods, which can explain these impossible maneuvers. Using this method will still leave a wake in its path and experience sonic boom, due to the fact air will always cluster in front of a fast moving object. For space travel, all it takes is altering this bubble to deflect molecules in front of it with the smallest amount of force which allows for unhindered travel through space. Crafts will still have to plot paths that avoid planets, asteroids, and stars unless they have enough power to enter alternative failed universe while they travel at ridiculous speeds.
As for propulsion, that is something I have no clue of how they could do it. They could either alter space and time around them so they instantly appear on the other side of their destination or stepping out of our universe bypassing all planets, stars, and asteroids in their path. There are other ideas such as teleportation that like Battlestar Galactica, Hyper Space such as Stargate SG-1, or FTL travel like in Star Trek which is called Warp Speed.
I think the most plausible travel is FTL, because it could be possible with protection such as Gravity Bubbles or Shields but they will still have to avoid planets and stars along their path.
A man's ethical behaviour should be based effectually on sympathy, education, and social ties and needs; no religious basis is necessary. Man would indeed be in a poor way if he had to be restrained by fear of punishment and hope of reward after death. - Albert Einstein
I like the idea that they can manipulate gravity like magnetic force, so that they can balance it out in order to hover motionless, just like magnets repelling each other, and then perhaps magnify the repulsion so that that's how they can suddenly scoot off at great speed. Perhaps for deep space travel they can use a similar technique, although obviously the gravitational forces would be so much weaker so they'd probably have to have some means of magnifying it.
And yes, the idea of a 'bubble' of vacuum while within atmosphere, perhaps created by repelling air molecules, would solve problems of surface friction. Perhaps somehow they can float in zero G within that bubble.
Of course, if the craft that people see aren't manned, that would solve problems of G force anyway.
Life is a hideous business, and from the background behind what we know of it peer daemoniacal hints of truth which make it sometimes a thousandfold more hideous.
Everything is still prone to the dynamics of our atmosphere! If E.T is running outside our physics then ITs all there Bad ! Like In Good Bad ! Like In Totally awesome Bad to the Bone ! I want one of those Rides !