IMO, the safest day to fly was the evening of December 31, 1999 on American Airlines. Everyone who's anyone in the aviation industry was probably double and triple checking everything to make sure nothing went wrong with the AA flights that carried the FAA administrator from Washington Dallas and San Francisco.
Other than that, its more difficult to determine, as its a combination of weather, equipment, ground and fight crew (fatigue), other passengers (air rage), the controllers (fatigue), air traffic congestion, security (hijack, bomb), and sheer luck. Keep in mind that something in another aircraft can also affect the safety of your aircraft, or ruin a perfect day at home.
Also, ground traffic to and from the airport (crew, passengers, equipment, etc), and foot traffic on the airport grounds can also be hazards...
What I'm trying to say, in a rather strange way, is that if the only problem I've had during today's flight is a few FA's in first class while I'm stuck in the center seat in economy next to a non-stop cougher and a non-stop chatter, yet I can go home to my family at the end of it and maybe log on and file a trip report, it has been a safe day for me.
[This message has been edited by Indurain (edited 02-02-2000).]