About 100 Southwest Airlines flights were canceled across the country Monday morning, including 12 out of Midway Airport.
Southwest is slowly returning its jetliners to service Monday and Tuesday after surface cracks were found in three more planes overnight.
By mid Monday afternoon, most flights had returned to normal schedules with only a few departures running a few minutes late.
The cracks are similar to those officials suspect played a role in the tear that caused a Boeing 737-300 to lose a six-foot chunk of its fuselage on Friday while airborne. The plane lost pressure and made an emergency landing in Yuma.
No one was seriously injured, but several people on board reportedly passed out from the loss of cabin pressure.
Since then Southwest grounded its 79 other Boeing 737-300s and began inspecting them.
Midway passengers waiting for their Southwest flights on Monday told NBC Chicago they're taking the delays in stride and are glad the air carrier is putting safety first.
On Saturday, about 40 Southwest flights were delayed Saturday after the airline grounded nearly 80 planes, forcing about 300 cancellations around its network.