Travis Barker's making the most of his first trip via airplane in 13 years by enjoying his new favorite thing ... getting frisky with Kourtney Kardashian.
The couple's currently on vacation in Cabo, and from the looks of things -- have picked up right where they left off in the States ... with no shortage of PDA.
We're told they were together for a while in the pool at the Las Ventanas al Paraiso resort and making out ... while enjoying tropical drinks in the agua.
Kourtney and Travis are staying in a very secure spot at the hotel, but they're clearly mingling with other guests in the main pool.
We broke the story ... Barker's trek to Mexico with his girlfriend -- along with Kris Jenner and Corey Gamble -- was his first time flying since the deadly 2008 plane crash that killed 4 people and left him with third-degree burns on 65 percent of his body.
After the crash -- in which the Blink-182 drummer lost 2 of his close friends, Charles "Che" Still and Chris Baker -- he vowed to never fly again ... but recently said he might give it another try.
That's exactly what he did this past weekend, and he's crediting Kourtney with helping him get there ... saying, "With you anything is possible."