• The engine sales increase coincides with a push by Boeing and Airbus to boost output of new planes.
• General Electric and Raytheon's Pratt & Whitney supply engines for some of the most popular jetliners.
• GE and Raytheon reported higher revenue from repair shop visits and spare parts businesses.

A recovery in air travel is lifting sales and repairs at the aircraft engine units of General Electric and Raytheon Technologies as Boeing and Airbus scramble to increase their production rates of new planes.

Sales in General Electric's aerospace unit rose 25% in the first quarter to $6.98 billion, the company said in a filing Tuesday. The unit makes engines for Boeing's 737 Max planes and Airbus' A320 family of narrow-body aircraft. The company said an increase in shop visits and spare parts helped drive up revenue for the unit.

Raytheon's Pratt & Whitney engine unit sales increased 15% from a year earlier to $5.23 billion. Its Collins Aerospace unit, which makes everything from avionics to aircraft interiors, rose 15% to $5.58 billion.

The improvements in those companies come as Airbus and Boeing are trying to increase their output of new planes for airlines. A surge in travel demand has also increased demand for new jets and maintenance on older planes.

Boeing will likely detail its plans for aircraft output and deliveries to airlines for the year when it reports quarterly results before the market opens Wednesday.

The company had planned to deliver around 400 737 Max jets this year. But earlier this month, Boeing disclosed a manufacturing flaw on certain 737 Max planes, its bestseller, and that problem could pause deliveries of some of those aircraft.

CEO Dave Calhoun last week said the problem won't change Boeing's orders from suppliers as it continues to target a production rate increase.