(fxcue news) - The Federal Aviation Administration or FAA is investigating the pressurization issues on a Delta Air Lines flight, which caused injuries to some of its passengers, reports said. The airline, meanwhile, apologized to its passengers, who experienced bleeding from the ear and nose. The Delta Flight 1203, which was traveling from Salt Lake City International Airport on Sunday with 140 passengers to Portland International Airport in Oregon, reportedly was unable to pressurize above 10,000 feet. The cabin pressure malfunction forced the pilots of the Boeing 737-900ER aircraft to turn around and return to Salt Lake City. Oxygen masks were not deployed, and around 10 people with ruptured ear drum or nose bleed needed further medical evaluation or treatment. After landing, the aircraft was taken out of service, but it was allowed to operate again the next day. The airline had claimed that its technicians worked on the pressurization issue successfully. The airline reportedly said, "We sincerely apologize to our customers for their experience on flight 1203. The flight crew followed procedures to return to SLC where our teams on the ground supported our customers with their immediate needs." The latest issue adds to the woes of the flight's manufacturer, Boeing, which has been under severe scrutiny for the past few years amid various safety concerns. Boeing's latest issues started with a January 5 incident, when a mid-cabin door plug on Alaska Airlines' Boeing 737-9 MAX airplane blew out in the middle of the flight, following which FAA grounded around 171 737 MAX 9 airplanes for inspections for several weeks. In April, the FAA announced an investigation into the emergency landing by Southwest Airlines' Boeing 737-800 flight after its engine cover fell off and struck the wing flap during take-off. Further, in mid August, the company paused flight tests for its new 777X jetliner and grounded the four-aircraft test fleet after finding damage in a plane's structure.