ftp://www.nuntius.co.uk/nat/MNPSA9/mnps9.pdf
All flights which generally route in an eastbound or westbound direction should normally be flight
planned so that specified ten degrees of longitude (20°W, 30°W, 40°W etc.) are crossed at whole
degrees of latitude; and all generally northbound or southbound flights should normally be flight
planned so that specified parallels of latitude spaced at five degree intervals (65°N, 60°N, 55°N etc.) are
crossed at whole degrees of longitude.
All flights should plan to operate on great circle tracks joining successive significant waypoints.