Is this standard? No. But it is standard that many companies want free photography.
My standard policy is that Nikon has to give me free gear. So far, Nikon has had a problem adhering to my standard policy.
So unless there is a really great benefit to the travel company to have a credit on their site I don't see how this is good.
Without knowing your travel company or its agreement with its photographers, it's tough to say what to do.
If these folks contacted, say Getty, do you think Getty would agree to this for free?
Getty charges ~$100 to $200 per picture for a royalty-free image like this. But Getty has only six royalty-free images that suit this topic.
Departures magazine is lifestyle editorial but the purpose of Amex Pub is to encourage people to buy stuff using their Amex card so Amex can make more money. Cheapest print ad in Departures print mag is ~$30,000 (1/3 page B+W) and that's just for one edition. The mag is also published in five other international regions and each region has multiple editions. It costs extra (tens of thousands of dollars) to advertise in another edition/another region.
Amex Pub is part of a multi-billion-dollar corporation and it produces five print magazines along with many other products. Each magazine has its own web site. Each site (with paid advertising) gets ~20(?) million views per month. Pictures are seemingly kept online forever?
Departures also sends out ~50,000 weekly e-mail newsletters (with paid advertising).
How did Amex Pub get to be such a profitable publishing company? Paid advertising and free content.
On one hand, this wealthy company should be ashamed of itself for expecting free handouts. On the other hand, a lot of its content, at least online, is just crappy fluff pieces with minimal value other than to fill empty pages; a great example of "fast and cheap".
Departures also does (or at least, did) paid photo assignments. A long time ago, I believe the space rate was about $400 per 1/4 page photo and ~$2,200 for a cover, against a ~$900+ assignment fee. And that was for just one edition.
I did jobs for the Canadian magazine of a well-known loyalty card. It paid, (9 years ago), ~$1,200, plus expenses, per job to produce an inside picture. My point is that these corporate mags have lots of money.
If your travel company can benefit (link to your site + maybe other information) AND you have the rights to license the pictures for free AND you have releases for any people in the pictures (if applicable) AND you licence for use only on the
Departures site, then it might be okay.
Although, the photographers don't benefit from their pictures. Why should they help out a multi-billion-dollar company?