Southwest, still reeling from last week's meltdown, just suffered another system glitch that grounded flights

• Southwest experienced a weather system outage, which disrupted flight schedules again.
• Pilots made announcements while passengers were waiting for the flight, some people tweeted.

Southwest Airlines was on Tuesday hit by a weather system outage, which grounded flights and caused disruption again for passengers.

Several people posted on Twitter about their flight delays, saying the pilot announced the weather system was down and the plane was unable to take off.

One person tweeted that they were sitting on the aircraft for an hour and a half and waiting to depart because of the issue. Southwest apologized in response.

Around 140 Southwest flights were canceled on Tuesday, while more than 1,500 were delayed, according to flight-tracking site FlightAware.

The airline told Insider in a statement on Tuesday that its third-party vendor IBM had a "brief outage in their service that provides weather data prior to Southwest dispatching flights."

Southwest added that it expected minor delays for the remainder of the night. In the statement, the company also apologized to passengers for the inconvenience and encouraged customers to check the flight status on its website.

Pilots are required to be aware of weather reports and forecasts before a flight commences, according to federal regulations.

The weather system outage came the same day Southwest said it had made "solid progress" to resolve passengers' problems with luggage, reduce flight cancellations, and process refund requests.

Following a bitter winter storm that swept across parts of the US over the holiday period, Southwest's flight schedule was heavily impacted for several days. Passengers faced flight cancellations and delays, while airports were flooded with missing baggage.

Southwest said on December 30 it planned to resume normal operation "with minimal disruptions."