If you are talking about the Tinker’s Tools found in the players hand book, then I don’t think you need to worry. The tools themselves don’t seem to be defined in the book, but the rock gnome tinker ability lists some things you can make with them. In particular, they’re tiny, clockwork, gadgets, so it seems reasonable to assume that tinker’s tools specifically refer to the tools you’d need to work with small mechanical devices, rather than large vehicles or fabrics.

More generally, just because the players can envision how to build something does not mean the characters can. Things like planes and, to a lesser extent, parachutes require a specialized knowledge of physics to get right and there’s no reason to assume the characters would have this knowledge, even the wizards. What’s more, in a world where dragons and griffons can fly, it’s perfectly possible that traditional aeronautic devices, like planes from our world, simply wouldn’t function.

You’re perfectly in your right as DM to say “No, you can’t build that thing.” That said, you should endeavor to give them both the in-character reasons “Those aren’t actually the right tools, physics doesn’t work that way in this world, and your character has no reason to think this would work” and the out of character reasons “I’m worried this will cause balance problems and make it hard for me to run a good campaign for you.” If you only tell them the in character reasons then the players will, naturally, view your reasons as obstacles to overcome, rather than a request to stop trying. On the other hand, an out of game request won’t cause any confusion, but in game reasons can make it go over better and are nice to have regardless.

If one of your players really wants to play a character who can build anything via mundane means, you could try working with them to find or make a class that focuses on just that and only builds level appropriate things in reasonable quantities (this means both not being able to build a bi-plane at level one and being able to build a jet pack when everyone else is getting flight spells).