United Airlines' parent company, United Continental Holdings, reported strong quarterly results yesterday, more than doubling the carrier's first-quarter profit to $292 million. Despite the operational challenges associated with the grounding of United's 14 Boeing 737 MAX 9 aircraft, the carrier reported a 6.2% jump in revenue.

United achieves second-highest on-time performance

The major headline from first quarter on-time performance (OTP) results is Southwest's abysmal 52% OTP. Southwest is clearly feeling the operational impact of 34 grounded MAX 8 jets and growing labor strife with the carrier's mechanics' union.

United finished second in on-time performance, behind Delta but ahead of American. First quarter operations tend to be more challenging due to winter storms. Hubs like Chicago-O'Hare (ORD) and Denver (DEN) are particularly vulnerable to snow-related cancellations.

D:00 is an operational metric that airlines use to measure the time the plane pushes back from the gate. Airport or weather delays that occur after the plane has pushed back do not count against a carrier's on-time performance. Airlines also use A:15 (arrival within 15 mins of scheduled time) to measure their operational performance.

14 United 737 MAX 9 aircraft remain grounded

Like Southwest and American, United had to ground its fleet of Boeing 737 MAX aircraft. United's fleet remains parked at Houston's two airports, Hobby (HOU) and Houston Intercontinental (IAH). The grounded MAX fleet represents less than two percent of the carrier's fleet, so United was largely able to absorb the loss in capacity.

In the first quarter of 2019, United became the first US carrier to operate the Boeing 787-10 Dreamliner. The new aircraft – equipped with Polaris and Premium Plus – will fly from Newark (EWR) to six European destinations this spring and summer. United also became the first carrier in the world to operate all three Dreamliner variants: the 787-8, 787-9, and 787-10.