FARNBOROUGH, England — Boeing Co. and archrival Airbus were caught in a fierce dogfight for orders at the Farnborough Airshow on Tuesday, with both aircraft manufacturers unveiling multibillion dollar deals.

Boeing appeared to be a big winner for a second day. It trumpeted another two big orders, worth a little more than $11 billion, for its remodeled short-haul 737 aircraft, but the deals are not firm and could theoretically unravel. Meanwhile, the European manufacturer Airbus unveiled its first firm multibillion dollar order at this year’s airshow.

The US manufacturer said GE Capital Aviation Services, the commercial aircraft leasing and financing arm of General Electric, has committed to purchasing 75 of the 737 MAX 8s and 25 Next-Generation 737-800s. The deal is valued at around $9.2 billion at list prices. Boeing also said Kuwait’s ALAFCO has is committed to buying 20 of the 737 MAX 8s. Airbus said Cathay Pacific has put in a firm $4.2 billion order for Airbus’s long-haul A350-1000.