ITV News has been told that the squadrons have been working over-time and are having to cancel leave as they embark on back to back tours to Afghanistan and Libya.
The combination of stress and fatigue is potentially dangerous for those in charge of powerful fighter jets.
The causes of the crash are to be fully investigated in due course.
A vessel has gone out to the crash site to locate the wreckage ahead of a salvage operation.
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Their numbers swelled to about 5,000 as they set out walking towards the Mexican town of Tapachula.
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