I travel quite a bit too. Here are some of my recommendations; hopefully some are new titles or authors for you....
My favorite is Douglas Preston and Lincoln Child's Agent Penderghast Series, starting with 'The Relic', Douglas Preston's solitary novel 'The Codex' is also good I just finished it and gave it to my parents to listen to.
I also have enjoyed: James Patterson the Alex Cross Series and the Woman's Murder Club, Catherine Coulter's FBI series (not so much books 1 and 2 but I think I'm on book 12 now and they keep getting better and better), Nevada Barr's Anna Pigeon Series - the writer is a Park Ranger and each novel/mystery takes place in a National Park (so far I've only disliked one, I believe it was called 'Burn' which was set in New Orleans), J.A. Konrath's Jack Daniels series is terrific and very suspenseful. I admit this is a series I did read all except book 3 I think - 'Rusty Nail' which I did get through the system on audio - I just couldn't wait for the audio's and ordered the books that's how good they were to me, Kathy Reichs 'Bones Series' is always a good listen as is Patricia Cornwell's which is quite similar (both main characters are medical examiners). Clive Cussler is another favorite, I particularly love his Numa Files Series, Dirk Pitt Series and Fargo Adventure Series. He also writes an Oregon Files series but sometimes there are quite a few characters to keep track of, as well as a Isaac Belle series set back in the day which the first 1 was miserable slow, although 'The Spy' in that series which I think is the 3rd was better. Lastly Richard Castle's Nikki Heat Sereis is decent and I really enjoy the J. D. Robb (Nora Roberts) Murder series is terrific, the reader does a great job of pulling you in (these I often end bringing in so I can keep listening while I prepare dinner or clean the house - I think I'm up to 22 and have gotten all on CD through the system, the first 18 are also set up in abridged packs of 3 books, so collection 1-6 when you search; 15 CD's/collection which is also nice)
There are a couple good, random mystery books that also stick out that I've listened to including:
Plum Island by Nelson DeMille (I haven't liked all his books but this one was particulaly good, I do also believe I listened to it on audio cassette so I'm not sure if it's on CD)
The Amber Room by Steve Berry (he has several but this one I listened to recently and felt it would be worth ordering more by this author in the future)
On the Street Where You Live by Mary Higgins Clark