By David Shepardson WASHINGTON (Reuters) – Boeing Co does not anticipate winning regulatory approval its 737 MAX 10 before next summer, according to an letter from the Federal Aviation Administration (FAA) sent on Monday. Boeing faces a December deadline to win approval for the MAX 10 as well as another 737 variant, the MAX 7. Without an extension, Boeing must meet new modern cockpit-alerting requirements that could significantly delay the planes’ entry into service. “With regard to the 737-10, Boeing’s current project plan timeline has the 737-10 receiving an amended type certificate no soone…