John Mayer celebrates 31st birthday with Jennifer Aniston

John Mayer rang in his 31st birthday at exclusive Beverly Hills cigar bar Grand Havana Room October 15 - with back-on girlfriend Jennifer Aniston by his side.

The relaxed pair hung out on a private outdoor patio for several hours late in the evening. Mayer, at one point, affectionately stroked Aniston's hair.

The singer - whose actual birthday is October 16 - and the Marley and Me actress, 39, began a whirlwind romance in April, but split in August.

On October 10, however, the two appeared to be back on. They took in a Ray LaMontagne concert in Boston and then spent the next couple of days in New York City before flying to Los Angeles on a private plane.

Another public date followed on October 13, where they dined and drank wine with three pals at Sunset Tower's Tower Bar.

"They were holding hands at one point and seemed very much back on," a witness tells Us.

A source says the two reconnected because Aniston "can't deny their major chemistry, similarities and ability to laugh at things." via