Midway Airlines set up a luncheon for 450 today in the middle of the lobby of Midway Airport without disturbing a soul.

If Midway Airlines is successful, however, the lobby will bustle with airline passengers in the future, not diners.

The luncheon celebrated the inauguration of Midway's scheduled service from Chicago's little used airport to Cleveland, Detroit and Kansas City. Thursday, Midway Airlines will begin service of the nation's newest airline and the first all-jet interstate airline to be created since the Airline Deregulation Act.

Midway will operate 184 flights a week, using DC-9 aircraft, at air fares that are 25 to 50 percent less than competitors' flights to and from O'Hare International, a congested airport Midway officials hope prospective passengers will want to avoid.

Marvin F. Cohen, chairman of the Civil Aeronautics Board (CAB) told Midway's well-wishers here that "the commencement of service . . . brings together in one operation so many of the promises of deregulation -- new entry, satellite airport development, low fares and innovative services."

The festivities started this morning when Midway's three planes -- bright stripes of navy, yellow, orange and red on white -- arrived within 15 minutes of each other, bringing civic leaders from the three cities the new airline will serve.

"It was a pleasure not to be held up at O'Hare," Jack E. Reardon, mayor of Kansas City, Kan., said after the easy arrival.

Midway Airport was once the world's busiest, accommodating 20 million passengers a year before the airlines abandoned it in 1973 for O'Hare. Only Delta Airlines continued service there with three flights a day.

City officials who have supported the airport's revitalization hope that Midway's low fare service will bring more business to the airport and to the southwest area of Chicago, where it is located.

Midway Airlines said that response has been so enthusiastic over the low rates that many flights are already sold out and waiting lists have been started.

As an example of the savings, Midway offers a regular coach fare to Kansas City of $55 and a fare of $37 for all weekend flights and some off-peak weekday flights. The two unrestricted fares compare with a $79 coach fare of its O'Hare competitors.

"As someone whose monthly job is to explain what has happened in the past months to the Consumer Price Index, I find this is a particularly happy occasion," Alfred E. Kahn, President Carter's chief inflation advisor, told the gathering here today. Kahn served as chairman of the CAB when it gave Midway federal permission to operate as an airlines into Midway airport.

"I hope you make a billion dollars," Kahn told Midway president Irving T. Tague.

Kahn sported a Chicago tie given him by Chicago's aldermen the week after he blasted them for taking a 40 percent increase in pay that he said violated the wage-price standards. Kahn gave President Carter credit for supporting deregulation of the airline industry, which Midway officials say allowed them to get started.

"So you see, my wearing my Carter-Mondale button is not a political act," he said. "It is a historical statement."

Conspicuously absent was Chicago Mayor Jane Byrne, who was scheduled to take part in today's activities but canceled to hold a press conference to endorse Sen. Edward M. Kennedy for president.

Midway President Tague says the airline expects to carry about 700,000 passengers during its first year and nearly double the second year. In the spring, the airline will take delivery of two more planes. It is considering adding Midway services to Washington, D.C., and Minneapolis-St. Paul.