If there are no quality .com available domains suited for my travel startup, is it too bad to use a .org or .travel gtld?

That one question entails several separate answers.

.TRAVEL is little used and practically unknown to the general public, even though it has been around for 7 or 8 years. Partly that's because the .TRAVEL registry mandates a special application process that confines use of the extension to particular kinds of entities.

Have you ever visited a .TRAVEL website? Most people have never seen one. And so, with negligible public adoption of .TRAVEL, you'd find yourself almost entirely alone explaining your name / web address over and over again. Names that require long explanations are cumbersome and forgettable.

There's an added burden with vanity extensions such as .TRAVEL. Suppose you name your company or website "Exotic Travel". If you use Exotic.Travel because ExoticTravel.com is too expensive or else in use already, then you will either face a competitor who uses ExoticTravel.com or else you will need to purchase and maintain both domains. Owning a vanity extension without a matching .COM is almost always a bad idea. Some major websites have learned that the hard way -- often paying 5 or 6 figures to acquire the .COM domain they hoped to circumvent.

I'm not a .COM purist. In fact, I'm fond of some domains in vanity extensions. But they should be used as a pair with the .COM most of the time.

.ORG can be ideal for certain kinds of projects. But it's impossible for me to give an answer without knowing the name in question. If .ORG is part of the brand identity -- meaning that you're proud to display the .ORG -- then it can work. Nonprofits are especially well suited to .ORG for this reason, as are some other websites. However, if using the .ORG is merely a cheap knockoff of your first-choice domain, then people will perceive it rightly as just a cheap knockoff. We'd have to discuss the name specifically for me to give any meaningful feedback, though.

Of course, you began by saying "there are no quality .COMs available". Frankly, that's probably not true. Availability comes in all shapes and sizes. It's certainly the case that most of the good .COM domains already belong to somebody. After all, the internet has been around for a few decades. Just as with the North American continent, every vacant lot has an owner by now. But many good .COMs, though owned, are nevertheless not in use -- and therefore available, depending on your budget.

It's dangerous to settle for the first .COM you find that's available for $10. Almost by definition, those are precisely the domains that have interested nobody alive at all for 20+ years. However, I've been exploring the name space every single day full time for some years now -- often for myself but frequently for clients. And a small percentage of good domains do remain available. However, it takes experience to find them and tell the difference between fool's gold and the genuine article. With my last naming client, I'd say that less than 1% of my name ideas were unregistered.

That's a long answer. Since it's now 1:17 a.m., I'd better cut things off at this point!

As one of my industry colleagues said: If you think all the good domains are taken, you don't understand branding. Think about naming your agency, not describing it. We easily find 100 free .com domains on every naming project.. and often a lot more. With names that sound like they should be in the dictionary.
And yes, soon all the new domains will be here...like .web or .shop or .online or... BUT BUT trademark rules will apply even more than before - and trademark rules govern domain rules. So please make sure the trademarks are clear before you pay for any domains. By this time next year it will be very acceptable to have a non .com domain name. May even be cool to be a .buzz or a .cool!

You can use a custom ending if it can tie in to your company/brand name. visual.ly is a good example.

With browser history and personal settings it's much less an issue than is used to be.

Before you pick a final name please conduct a keyword search and determine what keywords are important for your industry. One of the most powerful ways to get found on the internet starts with your URL. If you can add or mix and match keywords that have a high monthly search...you will probably be better off then trying to secure a cute name.