However, considerable discretion is allowed in emergency situations, with ATC's mandate being to help as much as possible and keep the crew's workload lower, regardless of normal operation rules. If ATC understands there to be an emergency, they may ask the crew to clarify but they aren't going to insist "You must say 'mayday' three times."

Somewhat related to callsign confusion is the phonetic alphabet's D = Delta. This would obviously cause confusion at Atlanta. The trams in the terminal use "David"; I believe ATC uses "Dixie".