From a USA TODAY Article 10/31/2005:
Memorable flight numbers
Searching for superstitious behavior in airline flight numbers uncovered another story about memorable flight numbers. Flights to Las Vegas with 7s and 11s are not only alleged to bring good luck, but they are also easy to remember. (Related column: Check your travel superstitions, or carry them on?)
More airlines might want to use those same easy-to-remember flight numbers, but the Federal Aviation Administration limits the number of similar flight numbers flying into the same place at the same time to avoid confusion in the control tower.
Airlines find many ways to make flight numbering somewhat systematical and therefore memorable.For example, most airlines assign even flight numbers to eastbound and northbound flights, while westbound and southbound flights are assigned odd numbers. Airlines will usually assign four-digit numbers to flights flown by their regional, commuter or other affiliates and these four-digit numbers will usually be higher than any number used by the main line service of that carrier. For example, all Delta Airlines flights are numbered between 1 and 1974, while Delta's subsidiary Song is assigned the range of flight numbers between 1975 and 2099, and flight numbers 4838 to 5912 are assigned to regional carrier Comair.
The same is true of codeshare flights. So a codeshare flight 1139 on United Airlines, which is designated as flight 5112 on Air Canada, is actually operated by United Airlines, while Air Canada flight 560, which is the same flight offered by United as flight 8253, is really operated by Air Canada on the same route between Vancouver and San Francisco.
In some high-frequency markets airlines will assign a sequential series of numbers based on departure time. For example, between Washington and New York, US Airways shuttle flight 2158 departs at 6 a.m., 2160 at 7 a.m., 2162 at 8 a.m., etc., and Delta shuttle flight 1938 departs at 6 a.m., 1940 at 6:30 a.m., and 1942 at 7:30 a.m., etc.
American, Continental, Delta and Northwest Airlines all offer an unforgettable flight 1776 to Philadelphia. And American and Continental Airlines both offer a flight 1492 to Columbus.
A very creative scheduling department at AirTran has implemented a flight 303 to Denver, which is the area code for the Mile High City, and a flight 435 to Kansas City, which is the number of a major interstate highway there, according to spokeswoman Judy Graham-Weaver.
Historically, airlines have done very creative things with flight numbers, according to Bob Distler, an aviation consultant and member of the Washington State Transportation Commission, who formerly worked for Pan American Airways as managing director of scheduling and planning.
Numerous carriers have operated flight 1849 or 49 to San Francisco, after the California gold rush, Distler says. In the early 1960s, American designated its 6 p.m. flight from New York's JFK Airport to Los Angeles as flight 21 to highlight its first-class catering by The 21 Club. That catering is long gone, but flight 21 still departs JFK for Los Angeles at 6 p.m. every day.
Many airlines have used Flights 1 and 2 for a featured service or on a premier route. Examples include National Airlines' Miami to London route, Pan American's round-the-world service, Qantas' first Boeing 747-238 service between Sydney and London, and British Airways' first Concorde flight to JFK.
When Distler was with Pan American, the airline received permission to change the number of flight 100 from New York to London to 1776 and do a low flyover above the tall ships in New York Harbor on the nation's bicentennial on July 4, 1976.
Alaska Airlines numbered its Seattle to Anchorage flights with an 1890 series to commemorate the Alaskan gold rush. And Mohawk Airlines used the same sequence of flight numbers for its DC3 "Gaslight Service," linking LaGuardia with upstate New York in the early '60s. Those flights featured cigars, pretzels and a special beer from upstate New York. The airplanes were even painted in a unique livery with a gaslight on the tail according to Distler.