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FORT WORTH, Texas (Reuters) - The acting head of the Federal Aviation Administration said on Wednesday he does not have a specific timetable for when the agency may unground the Boeing 737 MAX that has been involved in two fatal crashes since October.

“I’m not tied to a timetable,” Dan Elwell told reporters ahead of a meeting planned for Thursday with more than 30 international air regulators including China, the European Union and Canada. He said he plans to share the FAA’s safety analysis to date on Thursday, but said the agency is still waiting Boeing’s formal software upgrade and emphasized the FAA has not decided on the revised training requirements.