Here is a great optical illusion photo taken of a Lufthansa 747-400 and a United 757-200 that were on simultaneous approaches to runways 28L and 28R at San Francisco (SFO). The separation requirement for flying parallel and simultaneous approaches is 225 meters (738 feet). (That would be wingtip to wingtip. These two aircraft are at a safe distance for the approaches they are each flying. Due to the 747 being three times larger than the 757, and being slightly behind will give us this incredible optical illusion. Someone not familiar with aviation may very well see this and make an assumption that these two aircraft are only inches apart.