Boeing won’t launch a new jetliner any time soon to address Airbus’ widening sales lead in the narrow-body market, Chief Executive Officer Dave Calhoun said.

Prominent customers like Air Lease Corp. founder Steven Udvar-Hazy have been calling on Boeing to get moving on the mid-sized aircraft family Calhoun tabled two years ago. But there are no leaps in engine technology in sight to propel jetliner sales, and Calhoun said he isn’t willing to bet an expensive new development program on the current generation of turbofans.

The Boeing chief is counting on new digital tools to revolutionize how aircraft are designed, built and tracked over decades in the commercial market, concepts the company has touted for at least five years. 

However, Boeing has been testing the technology on defense programs like the T-7 trainer and it isn’t yet “mature,” Calhoun said at the Bernstein Strategic Decisions Conference on Friday.

It will take “at least a couple of years before I’m confident that those tools are tested and mature enough to implement on the next airplane,” Calhoun said, citing an internal review he’d attended Thursday. “When that happens, then we design the next airplane. We don’t do it the other way around.”

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Calhoun reiterated that Boeing doesn’t plan to raise equity in the near term, and wouldn’t do so before 787 Dreamliner deliveries have resumed and the planemaker has tackled production issues with the 737 Max.