Boeing 737 MAX 9 planes have returned to the skies

• Alaska began flying Boeing MAX 9 planes again on Friday, the airline confirmed in an email to Axios.
• United Airlines resumed flying MAX 9s on Saturday, the company said.

Details: The FAA has required detailed examinations of their exit door plugs — the type of panel that flew off on Jan. 5 — plus inspections of specific bolts and fittings.

• The agency is also requiring the retightening of fasteners and fixing anything that's damaged or looks off.

Plus: The FAA isn't letting Boeing off the hook.

• In a written statement, FAA administrator Mike Whitaker said the agency won't let Boeing boost production of 737 MAX aircraft "until we are satisfied that the quality control issues uncovered during this process are resolved."
• "This won't be back to business as usual for Boeing," Whitaker said.

What they're saying: Boeing said in a statement that the company "will continue to cooperate fully and transparently with the FAA and follow their direction as we take action to strengthen safety and quality."