( CNN ) -- Just days after a Boeing 737 flown by Southwest Airlines made an emergency landing with a hole in its fuselage , the Federal Aviation Administration said in a press release Monday that it will mandate operators of about 175 specific older Boeing 737s to conduct inspections for wear and tear . The FAA said the `` emergency directive '' it plans to issue on Tuesday would affect about 80 U.S.-registered 737-300s , 737-400s and 737-500s , mostly operated by Southwest . The remaining 95 or so aircraft are registered outside the United States . Each of the 175 or so planes in question have taken off and landed more than 30,000 times and will receive repetitive electromagnetic inspections at regular intervals for fatigue damage . In a separate statement , Boeing said it was working with the FAA , the National Transportation Safety Board and Southwest , and it was preparing a service bulletin to recommend lap joint inspections on certain 737 models . NTSB board member Robert Sumwalt said Monday that inspectors have visually checked lap joints in the past , but have n't used high-tech monitoring , because no one thought that part of the plane was susceptible to cracks . Moving forward , inspectors will test the joints with an electromagnetic process . The chairman on the U.S. Senate Committee on Commerce , Science and Transportation said in a statement that the American public wants answers to retain confidence in commercial air travel . `` As the details of this unusual incident unfold , we will get a better understanding of what caused the plane 's fuselage to tear open , '' said Sen. Jay Rockefeller , D-West Virginia . `` I expect the FAA to be painstakingly diligent in reviewing the safety of all aircraft , and to conduct a careful investigation into what caused the cracks that have been discovered on the bodies of these planes . '' Rockefeller took advantage of the occasion to renew his call for reauthorizing the FAA . `` The FAA reauthorization bill now headed to conference takes steps to strengthen the inspection process of passenger aircraft , and I hope we can move that bill quickly to a resolution , '' he said . After Southwest canceled about 600 flights over the weekend to accommodate inspections , the airline said it canceled another 70 flights on Monday . By 3:30 p.m. Monday , the company had checked out 67 of the 79 planes it had grounded for inspection . Southwest said 64 of the 737-300s were being returned to service , while inspectors had discovered subsurface cracks on three jets . Those three will remain out of service `` until Boeing recommends an appropriate repair , '' Southwest said . As planes are cleared , they will be put back into service , Southwest said . Inspections are expected to be completed by late Tuesday . The airline recommended that customers should check with the website SWA.com for the status of a particular flight or rebook a trip before heading to the airport . Eighteen minutes into Flight 812 from Phoenix to Sacramento , California , on Friday , a hole 5 feet long and 1 foot wide opened in the fuselage , causing the cabin to lose pressure , the NTSB said . One flight attendant received minor injuries , the agency said . The pilot initially planned to return to Phoenix , but he made an emergency landing at a military base in Yuma , Arizona , after flight attendants reported seeing blue sky through the jet 's roof , the safety board 's Robert Sumwalt told reporters . Some of the 118 passengers who were aboard the crippled Boeing 737 said they feared for their lives . `` We were in shock , '' passenger Debbie Downey said Saturday . `` We were in row 16 , and my husband and I could see blue sky ... the wiring , the cabling . It actually was terrifying . '' Greg Hansen said fellow passengers panicked and screamed as the sun shone through the cabin . `` Most people were just white knuckles , holding on to the arm rests , '' he said . The airline said it provided a full refund , an apology and two complimentary round-trip passes on the airline for future flights . In July 2009 , another Southwest Airlines 737-300 made an emergency landing when cabin pressure dropped because of a football-size hole in the jet . That incident prompted the airline to inspect its entire fleet of 737-300s . Earlier that same year , the airline was fined $ 7.5 million by the FAA after the agency found that Southwest operated 46 of its Boeing 737s on nearly 60,000 flights without performing mandatory inspections for fatigue cracks in their fuselages . Sumwalt said the 737 used for Flight 812 had a maintenance check in March at Southwest 's Dallas facility , and the jet had no outstanding maintenance issues at the time of the accident , with all its records `` positive , up to date , ( and ) with no discrepancies . '' The plane 's flight data recorders had no noteworthy information on them , Sumwalt said . CNN 's Mike Ahlers , Ric Ward and Marnie Hunter contributed to this report .
NEW : Southwest Airlines says as of Eighteen minutes , it had inspected 67 of its 79 grounded jets . NEW : The joint where the breach opened had been visually , not electromagnetically , inspected in past . Southwest Airlines says it plans to mandate inspections of certain About 175 . 79 planes , including About 175 registered in the United States will be subject to inspection .