That's like asking what is the legal definition of 'wet'! Bit wishy washy. WHat would you consider 'Long Haul'? LHR-Nairobi? LHR-New York? LHR-Cairo? There are many definitions- I have seen SH 0-4hours, MH 4-8 hours, LH 8+ hours. Different countries have different needs for a relief crewmember, so there's no hard and fast figure there. Is it time or distance? Take your pick. The only real definition I can think of is Long Haul=a Long Way. I think you would have trouble pinning it down better than that. New York-LHR 6 hours? I'd put that as MH, but many would think of it as LH. No hard and fast figure because there is no hard and fast definition that would be accepted by all.