Since one has to purchase tickets in advance in order to attend, it seems plausible to suppose that the airport authorities actually do know how many people are likely to attend this weekend. In any event, a spokesman has warned readers of the Worthing Herald:
We are expecting very large crowds at this week’s RAFA Shoreham Airshow. This will inevitably cause delays on routes around Shoreham, notably the A27, A259 and A283. .. Car parking is available at Shoreham Airport and Adur Recreational Ground. On leaving the airshow, our staff will be trying to get everybody out of the airfield as quickly as possible but .. there will be delays at peak times. If possible, please stagger your journey home and enjoy the trade stands and attractions which will be open after the show.