Wreckage and debris has been strewn across half a mile of land
Inquiries are continuing by police and air accident experts into the crash involving two RAF light aircraft.
Two schoolgirl air cadets killed have been named as cousins Nikkita Marie Walters, 13, and Katie-Jo Davies, 14.
Both attended Tonyrefail Comprehensive, in Rhondda Cynon Taf.
The Air Training Corps cadets were on an RAF "air experience flight" with tutors Hylton Price from Bridgend and Andrew Marsh from Vale of Glamorgan, who were also killed.
Gp Capt Andy Naismith said the RAF felt it had lost "four of our close family".
A tight police cordon remains in place across the crash site, spread over a half a mile of land close to the Kenfig Nature Reserve.
The German-made two-seater Grob Tutor aircraft had been undertaking an air experience flight, which aims to give those interested in a possible military flying career a taste of the RAF's work.
The aircraft had flown from their base about 20 miles (32km) away at RAF St Athan in the Vale of Glamorgan on what was supposed to be a routine 20-minute sortie.
But eyewitnesses reported seeing the two planes collide and an explosion, before both aircraft crashed to the ground at about 1100 GMT.
Three investigations into the accident have now been launched, one by the police, another by the Air Accidents Investigation Branch (AAIB), and an RAF board of inquiry.
Aviation writer and air accident expert Jim Ferguson said the main focus at the moment was to recover "every scrap of wreckage", and track down all the eyewitnesses.
"One issue for the investigators is that these sort of planes do not carry black box flight recorders," he said.
"So without that detailed flight data, the investigation will rely on examining the aircraft remains, and taking detailed eyewitness statements."
South Wales Police have already asked that members of the public stay away from the crash site area, and if they do find any crash debris, to leave it in place and contact its officers.
Mr Ferguson also appealed for people to heed the advice: "The debris can be strewn across a wide area, and it is the best evidence the teams will have to pull together a picture of what happened.
"I would say to anyone who has come across any wreckage, even if they've picked it up and taken it home, please tell the police and let them do their job.
"Also, if you did witness the crash, please get in touch with the police, any little detail may be significant in discovering what caused this tragedy."
The crash scene was close to the M4 motorway
The UK's fleet of around 100 Grob Tutor planes are owned and maintained by a civilian company, VT Aerospace.
Mr Ferguson said all paper records relating to the two aircraft would now be "locked down" by investigators, as they examined them in detail.
However, the RAF said it had no intention of withdrawing the Grob Tutor from service at the moment.
The planes provide "elementary flying training" at three RAF bases, including the aircrafts' parent base, RAF Cranwell in Lincolnshire.
Gp Capt Andy Naismith from RAF Cranwell said he had taken the decision to keep the Grob Tutor planes flying.
"We've been flying the Tutor for nearly 10 years, and it has an absolutely outstanding safety record," he said.
"We are very confident of it. I am content, generally, to continue operating the Tutor ad infinitum."
As the investigations continue on site, Bridgend council said it had organised a number of community support services in the area.
Specially trained counsellors will be on hand at Kenfig Hill fire station to offer help to any members of the public who feel affected by the crash.
South Wales Police officers will also be on hand to take statements from anyone who witnessed the incident.
Anyone who witnessed the incident or has discovered debris should contact South Wales Police on 01656 306102 or 01656 306103.