Most flights from/to Houston use the following 7 airports
Conroe/North Houston Regional Airport
Houston
Timezone: GMT-6
CXO/KCXO
David Wayne Hooks Memorial Airport
Houston
Timezone: GMT-6
DWH/KDWH
Ellington Airport
Houston
Timezone: GMT-6
EFD/KEFD
William P Hobby Airport
Houston
Timezone: GMT-6
HOU/KHOU
George Bush Intercontinental Airport
Houston
Timezone: GMT-6
IAH/KIAH
West Houston Airport
Houston
Timezone: GMT-6
IWS/KIWS
Sugar Land Regional Airport
Houston
Timezone: GMT-6
SGR/KSGR