The 757 is according to the MTOM in the medium category. However due to the strong wake it produces it is considered heavy for the following aircraft.
The 737-800 as heavy? That's just a mistake of Spanish ATC.
If I'm correct, a 738 is indicated as 73H on the radar screen. The 'H' stands for '8', but some Spanish controllers mix it up with the heavy suffix.
I once heard the same mistake being made in Lanzarote.
Last edited by Bus Driver Man; 23rd Jul 2011 at 22:01.