Hobby Airport opened in June 1927 as a private landing field in a 600-acre (240 ha) pasture known as W.T. Carter Field. In the 1930s, it was served by Braniff International Airways and Eastern Air Lines. The site was acquired by the city of Houston and was named Houston Municipal Airport in 1937. The airport was renamed Howard R. Hughes Airport in 1938. Howard Hughes was responsible for several improvements to the airport, including its first control tower, built in 1938. The airport's name changed back to Houston Municipal because Hughes was still alive at the time and regulations did not allow federal improvement funds for an airport named after a living person.

The city of Houston opened a new air terminal and hangar in 1940.

Women Airforce Service Pilots (WASP) in 1943

The first three Women Airforce Service Pilots (WASP) training classes were held at the Houston Municipal Airport in 1943.

Airlines in the 1940s and 1950s

In June 1948, Braniff International Airways began international flights from Houston operated with Douglas DC-4 and DC-6s to South America via Cuba and Panama. In the June 1948 timetable, the airline had two flights a week to Havana, Cuba – Panama City, Panama (via Balboa, Canal Zone) – Guayaquil, Ecuador – Lima, Peru, and a third flight that skipped Guayaquil. In 1949, Braniff flew direct via Lima to Rio de Janeiro, Brazil, and La Paz, Bolivia. In 1950, Pan American World Airways (Pan Am) began nonstop Douglas DC-4 service to Mexico City. On October 1, 1950, Chicago and Southern Air Lines began flying new Lockheed Constellations nonstop to St. Louis and direct to Chicago Midway Airport. Chicago & Southern flew nonstop to New Orleans, the sole purpose being to connect to the airline's daily Douglas DC-4 "Caribbean Comet" flights between New Orleans and Havana, Cuba; Kingston, Jamaica, and Caracas, Venezuela, as Chicago & Southern did not then have local traffic rights between Houston and New Orleans. In 1953, Chicago & Southern (C&S) was acquired by and merged into Delta Air Lines, giving Delta access to Houston for the first time. In 1954, Delta, operating as "Delta C&S", was flying a daily Convair 340 Houston – New Orleans – Havana, Cuba – Port au Prince, Haiti – Ciudad Trujillo (now Santo Domingo), Dominican Republic – San Juan, Puerto Rico. Also in 1954, an expanded terminal building opened to support the 53,640 airline flights that carried 910,047 passengers. The airport was renamed Houston International Airport the same year.

The April 1957 Official Airline Guide lists 26 weekday departures on Eastern, 20 on Braniff (plus four departures a week to/from South America), nine on Continental Airlines, nine on Delta Air Lines, nine on Trans-Texas Airways, four on National Airlines, two on Pan American World Airways and one on American Airlines. There were nonstops to New York City and Washington, D.C., but not to Chicago or Denver or anywhere west of Colorado. Later in 1957, KLM Royal Dutch Airlines started Douglas DC-7C flights to Amsterdam via Montreal. In 1958, Delta was operating daily nonstop Douglas DC-7s to New York City and weekly DC-7s direct to Caracas, Venezuela, via New Orleans (Delta called this latter service the "El Petrolero") while Eastern Douglas DC-7s and Lockheed Constellations flew nonstop to New York City.

The jet age arrives

Houston's first scheduled jets were Delta Douglas DC-8s nonstop to New York in December 1959 (Cearley says they began on December 1). Braniff International introduced Boeing 707s in April 1960, nonstop to Dallas Love Field and direct to Chicago O'Hare Airport; Braniff Lockheed L-188 Electra propjets flew nonstop to Chicago Midway Airport and Dallas Love Field, and direct to Denver, Minneapolis/St. Paul, Kansas City and Lubbock. In June 1960, Eastern Airlines Douglas DC-8s flew nonstop to New York City Idlewild Airport and to Atlanta, in addition to Lockheed L-188 Electras nonstop to Washington, D.C. National Airport with one-stop Electras to Newark. In July 1960, KLM introduced Douglas DC-8 flights to Amsterdam via Montreal before moving to Houston Intercontinental Airport (now George Bush Intercontinental Airport), where they remain today with nonstop Boeing 787 flights to Amsterdam. On May 15, 1960, Delta Air Lines operated the world's first Convair 880 scheduled passenger flight nonstop to New York City Idlewild Airport from Hobby. Delta would introduce Convair 880 flights nonstop to Chicago O'Hare Airport, St. Louis and New Orleans from Houston in addition to its service to New York City.

In June 1961, National Airlines Douglas DC-8s and Continental 707s began flying nonstop to Los Angeles, and National Electras flew nonstop to Las Vegas, San Diego and San Francisco. These were Houston's first nonstops beyond El Paso. In 1963, Continental Vickers Viscounts operated a "milk run" multi-stop service on a routing of Houston-Austin-San Angelo-Midland/Odessa-El Paso-Tucson-Phoenix-Los Angeles while Continental Viscounts also flew direct to Lubbock and Amarillo. In summer 1965, American Airlines only had one jet flight a day from Hobby, a Boeing 707 flying Houston-San Antonio-El Paso-Phoenix-Oakland-San Francisco.