No cuss-laden outbursts here: Steven Slater is a Fanilow!

The famously disgruntled Jet Blue flight attendant was in a more cheerful mood on Saturday in Atlantic City, NJ -- where he attended Barry Manilow's "Symphony" concert with the New York Pops at Caesars Boardwalk Hall.

After the show, Slater got the VIP treatment -- meeting Manilow backstage for a photo op. Slater is a "huge fan" of the "Copacabana singer, a source tells

An instant folk hero to many, Slater quit his job before an August 9 flight; after arguing with a passenger, he gave an expletive-laden rant over the loudspeaker, activated the emergency chute and slid down with two beers in hand.

One celeb who's not so enthralled by Slater: Donald Trump. "What he did was despicable," Trump told The Insider Thursday. Trump argued that Slater "could have caused a major catastrophe...[he] is obviously not very stable. I think he's a wacko. I think he had a [disagreement] with someone close to him and he let it out on the passengers...I think we should stop celebrating him pretty quickly."