One of the things that kept many travelers open to flying again was airlines blocking off middle seats. As the airline industry continues to regroup, airline carriers are slowly getting rid of the option in hopes of filling planes again.

According to a press release, Southwest Airlines will begin filling its planes again in December. The airline has sold limited seats on each flight since the beginning of the pandemic.

“This practice of effectively keeping middle seats open bridged us from the early days of the pandemic, when we had little knowledge about the behavior of the virus, to now,” the airline said in a statement Thursday. “Today, aligned with science-based findings from trusted medical and aviation organizations, we will resume selling all available seats for travel beginning December 1, 2020.”

Southwest will join industry rivals American Airlines and United with this decision. As of now, Delta is one of the last U.S. based carriers to continue blocking middle seats.

“We are encouraged by modest improvements in leisure passenger traffic trends since the slowdown in demand experienced in July,” Southwest CEO Gary Kelly said in a statement. “However, until we have widely-available vaccines and achieve herd immunity, we expect passenger traffic and booking trends to remain fragile.”

Related: United Is The First US Airline To Offer Covid-19 Testing At Airport