Over 150 flights were  canceled and over 600 delayed before 9 a.m. Monday, the busiest Independence Day weekend since the beginning of the COVID-19 began

United Airlines canceled 34 flights and delayed 64 so far Monday; American Airlines canceled 19 and delayed 63, and Delta has canceled 15 and delayed 75

Adding to the mayhem was a computer glitch in American Airlines' staffing systems that left 12,000 flights without pilots beginning July 3

On Sunday alone, the Transportation Security Administration screened nearly 2.1 million travelers at airports across the U.S.