Love in the air for Katy and Orlando?

The 'Firework' hitmaker was on hand to help her rumoured new boyfriend take five-year-old Flynn - the actor's only child with ex-wife Miranda Kerr - to celebrate the fourth birthday of Robert Downey Jr.'s son Exton and she and the little boy got along well on the drive from Los Angeles to Malibu.

A source told Us Weekly magazine: ""Katy was entertaining Flynn so he wouldn't get bored.

"It was a long drive and she was talking to him and making him laugh."

Though they all attended the party together, the 31-year-old singer kept her distance to allow the 39-year-old hunk time to bond with his little boy.

A source said: "The birthday party had a Jurassic theme and there was a giant obstacle course and balloon maker.

"Orlando was really focused on Flynn and walking around the party holding his hand. Katy stayed behind them most of the time and let them do their thing."

Katy and Orlando first sparked speculation they were dating when they appeared close at a Golden Globes afterparty last month, and have been spotted together a few times since then.

However, it has been claimed their romance isn't serious yet.

A source said recently: "She's having fun with Orlando.

"I don't think she's seeing this as long-term yet. It's a fun hook-up thing right now."