Of the 6 million travelers, they're expecting approximately 550,000 travelers per day and more than 500 flights per day out of Houston's George Bush Intercontinental Airport.
According to Houston Airports, IAH will undergo a planned upgrade "designed to strengthen safety and extend the life of critical airport infrastructure."
The ground delay has been issued at Bush Airport until 2 p.m., according to the FAA website.
On Thursday, President Donald Trump announced that he will be signing an executive order instructing newly sworn-in DHS Secretary Markwayne Mullin to pay TSA agents immediately, ABC News reported.
H-Town's Bush Intercontinental Airport has become the symbol for how the ongoing partial government shutdown has wreaked havoc on the nation's air travel system.
Another day of long lines at Houston airports brought fewer headaches Wednesday, though travelers were still feeling the effects of earlier disruptions.