Just before Ed Harris shoots at Charles Bronson with a machine gun, you can see the unexploded squibs on the truck behind Bronson.
When the guns fire at the funeral you hear the sound of guns firing, but there is no sign of recoil or smoke coming from the rifles.
Aboard a 2-engine aircraft (outside shot) flying into the sunset the scene changes to an inside shot as Bronson climbs a stair case to an upstairs lounge -- not available on any Boeing 2-engine aircraft. The next outside shot is, indeed, of a Boeing 747, 4-engine plane with an upstairs lounge.