Just anything more than a paper on the mailbox. That has been the "training" to reduce area separation to 5 NM, a paper on the mailbox. According to that I can clear a C550 5 NM behind a B747... funny. 2 days ago A320 requested 1 NM off track to aviod wake turbulence of another A320 10 NM ahead, can you imagin with 5 NM and a heavy ahead??? And 440 kts of ground speed, thatīs less than 45 seconds separation, will be interesting.