Boeing has told suppliers it will resume production of its best-selling 737 jets at a rate of 52 aircraft per month in February 2020, and will then step up to a record 57 jets per month in June, people familiar with the matter told Reuters.

Boeing told more than 100 suppliers during at least one web meeting on July 30 that the new schedule depended upon regulators approving the 737 MAX to fly again commercially in the fourth quarter.

Boeing mainly builds the latest version of its cash-cow single-aisle family at its Seattle-area factory, but also builds a small number of earlier or military variants of the 737.

One of the people expressed skepticism over the timing given the intense scrutiny from regulators that grounded the 737 MAX after deadly crashes killed nearly 350 people in Ethiopia and Indonesia in the span of five months.

There is no guarantee when regulators will clear the 737 MAX to fly again, and Boeing Chief Executive Dennis Muilenburg told analysts last month that Boeing would consider further 737 output cuts or potentially suspending production if the grounding dragged on. 

In April, Boeing cut the number of 737s it produces monthly to 42 from 52 after halting deliveries to airline customers, cutting off a key source of cash and hitting margins. 

Because the grounding happened when Boeing was going up towards record production levels, and each move of the sprawling supply chain has to be planned far in advance, Boeing and its suppliers are now caught between two conflicting pressures: preparing to get back on the upward path as soon as the plane is flying but also ratcheting downwards if regulators stall and the grounding continues for longer than expected.