Samuel J. Solomon, 78, a founder and former president of an airline whose interests included low-cost transportation for large numbers of people, died Thursday of a heart attack.

He was stricken in an automobile while going to attend the funeral of a friend. He was pronounced dead at Suburban Hospital in Bethesda.

Mr. Solomon, who was born in Washington and lived in Silver Spring, began his airline career in 1933. He was one of a group, including Amelia Earhart, Gene Vidal and Paul F. Collins, which started Boston-Maine Airways.

In the same year, he became general manager of the old Hoover Airport, located on the site of what is now the Pentagon parking lot and the predecessor of National Airport.

In the late 1930s, Boston-Maine merged with National Airways and became Northeast Airlines. At that point, the line began serving the lucrative New York-Boston run.

Mr. Solomon was president and chairman of the board of the company during World War II. He also headed the Airlines War Training Institute, which trained pilots for military service. FOr his services, he was awarded a Certificate of Merit.

By the end of the war, Mr. Solomon had left Northeast. He started Atlantic Airlines, with the purpose of providing low-cost transportation in the northeastern United States. The Civil Aeronautics Board refused to approve the rate structure proposed by Mr. Solomon, and the project failed.

In the late 1940s Mr. Solomon became president of California-Eastern Airways and remained with it until 1956. In this period he also attempted to acquire control of D.C. Transit. That company was taken over by O. Roy Chalk.

Mr. Solomon then organized avemco Corp. which specializes in aviation insurance and the financing of aircraft purchases. He retired as president of the company in 1965, but remained a director until his death.

Mr. Solomon was a graduate of Central High School, in D.C. He served briefly in the Army during World War I and then went to work for the Treasury Department. In 1923, he went into the building business and remained in it until he switched to airlines.

He was a director of the YMCA in Washington for more than 40 years and was a founder and past president of the Argyle Country Club in Silver Spring.

Survivors include his wife, Alma Garber Solomon, of the home in Silver Spring; three sons, Richard J., William S. and Robert F., all of Silver Spring; a sister, Mary Hunt, of Albuquerque, N.M., eight grandchildren and one great-grandchild.