Up to 200,000 people are expected to flock to the Royal International Air Tattoo this weekend.
Traffic chaos is likely in the vicinity of RAF Fairford – including the A419, A417 and other roads in north Wiltshire and the Cotswolds that connect motorists with the event location.
The showground opens from 7.30am until 6pm on the Friday and from 7.30am until 7.30pm on Saturday and Sunday – with significant delays expected on some routes.
Route signage and messaging will be in place for all air tattoo traffic, and National Highways is advising motorists to be aware of increased volumes on the A417/A419, together with M5 junction 11A and M4 junction 15, as people make their way to the event.
Kathryn Wiltshire, South West Network Planner for National Highways, said: “The network is likely to see higher traffic volumes and the Fairford event is expected to see increased volumes on the A417 and A419, and potentially increased traffic around M4 junction 15 and M5 junction 11A.
“Our aim is to keep the National Highways network running while keeping all road users safe and informed, and we’re advising all drivers to check our traffic and travel information channels, to plan ahead and allow plenty of time for their journeys.”
Swindon Borough Council has also warned motorists about the potential of heavy traffic.
It said: “If you’re travelling around Swindon this weekend, remember that The Royal International Air Tattoo is scheduled to take place in Fairford.
“This means roads will be especially busy to the north of the town, with diversions in place to allow for event traffic.
“When travelling, to the show or elsewhere, be sure to check for any routes and diversions before you leave for your journey.”