Passengers were experiencing significant delays at Sydney Airport late on Wednesday after a storm knocked out a number of radio frequencies, cutting some communication between planes and the control tower.

Airservices Australia, which manages the country's air space, said there were "significant delays" to flights during the late afternoon peak and planes had been placed in holding patterns above Sydney for up to an hour.

Aircraft due to depart had also been affected by the outage, which began to occur as the storm intensified shortly before 4pm.

From midnight until 5.40pm on Wednesday, there were 1425 lightning strikes (ground and cloud events) recorded within a 50 km radius of Sydney's CBD, according to Weatherzone.