Darren Blakeman, who was watching the display, described what he saw: "We watched nine Red Arrows take off, then they did an approach from the south of the runway, they did a little display.
"After that display only eight of the airplanes landed and then there was a big siren went off at the airport, like an emergency sound, and there was a big yellow fire truck parked in the viewing area and then that rushed off with its blue lights going.
"From my scene here I can see a police helicopter and a coastguard helicopter and they're hovering in the air above the site."
A Ministry of Defence spokesman said: "We can confirm that we are aware of an incident involving one of the Red Arrows and we are investigating."