Another unidentified aircraft, possibly the same one, was also spotted over the Llyn Peninsula.
Some suggest the aircraft could be a commercial flight circling the sky while it waits for clearance to land at a nearby airport.
But a search of two real-time flight information websites found no sign of any aircraft flying over North Wales at the time, the Daily Post reports .
A motorist said: "The aircraft was flying in wide circles as I drove along the A55.
"It made a couple of wide circles and then headed off towards the west.
"I stopped in a layby at Rhuallt to take a picture on my mobile phone."
Tweeting a photograph Sandra Barford of Nefyn said: "Weird.. flying in circles over Pwllheli ."
She added the picture was taken at about 9.25am and it appeared there were two aircraft.
Three Hawk aircraft were airborne from RAF Valley this morning but their flight paths were further south and mostly overland although one was seen flying north towards the Isle of Man.
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Aviation expert Tony Simpson said commercial aircraft circling is unusual suggesting the normal explanation is that there may be a technical problem and is put in a circular holding pattern while the pilots try and sort out the issue.
He added: "But it may be the aircraft is approaching a busy airport earlier than expected and is marking time further away than the usual holding areas."