Simplify the following text for a Grade 8 native English-speaking person.
Original: On F1 race day a large number of spectators travel to the circuit by helicopter : enough to make Silverstone Heliport the busiest airport in the UK for this day .
Simplified: On F1 race day many spectators travel to the circuit by helicopter . Silverstone Heliport is the busiest airport in the UK for this day .