Up to 100 jets, helicopters and aeroplanes from a range of different eras across the RAF's history, including Spitfires and modern state-of-the-art aircraft, are expected to take part.
But how has the spectacle been organised and planned? Here are some of the questions surrounding the event on 10 July, which will be live streamed on Forces TV (Sky 450, Freeview 96, Freesat 165, Virgin 277) and on Forces News' Facebook page.
He also said operational commitments of the aircraft are another reason why they might not take part, as is the serviceability of each one.
How will it all happen?
It is expected the flypast will begin to form up over Suffolk to the west of Ipswich at around 12.45pm, 10 July, before heading towards Colchester, and then Chelmsford.
The formation will continue over the M25, Stapleford Abbotts, Hainault Forest and on to central London - passing the Olympic Park, Hackney, Bethnal Green and Shoreditch before getting to The Mall at around 1pm.
Wg Cdr Gatland said: "The front aircraft, the helicopters, are doing 90 knots, so about 100 miles an hour, the back aircraft, which will be the Red Arrows, are doing about 300 knots - just over 300 miles an hour.
"They obviously compress, they are at their tightest when they go over Buckingham Palace with a 30-second spacing in between.
"At that point we need to geographically deconflict them all safely using height, track lines away from each other and timing to keep them all clear."
How high will the aircraft be flying?
Wg Cdr Gatland said they will be stacked between 1,000ft and 1,200ft above the ground. He said their heights are alternated "through wake turbulence" and to provide space if the aircraft "happen to get too close".
How has it been planned?
The event has been planned using what Wg Cdr Gatland called "fantastic" and "very accurate" software in which speeds, routes and locations are entered and calculated.
They have also conducted flights over the planned route to check for obstructions - including any new tall buildings or cranes on top of buildings that have been newly erected.