(Reuters) - Senior Plc (>> Senior plc), an aircraft and auto parts maker, said first-half pretax profit rose 22 percent, boosted by higher demand from the growing commercial aviation sector.

The maker of hydraulic components, seal assemblies and aircraft wall panels said its large commercial aircraft market, which represents 39 percent of group sales, saw a robust growth in the first half.

With the U.S. airlines replacing old models, and airlines from the Gulf to Asia expanding their fleets to serve new markets, demand for Senior's products has increased.

Senior's aerospace division generates two-thirds of the company's total revenue.

Boeing and Airbus collectively delivered 645 aircraft in the first half of this year, 7 percent more than the prior year.

Net orders from the aviation giants increased 22 percent to combined order book increasing to 10,783 aircraft.

Senior also said group Chief Executive Mark Rollins would retire in the first half of 2015 after seven years on the job. The company said it started the process to recruit a new CEO.

"There should be nothing untoward with respect to the announcement of the CEO stepping down, although it will garner attention," Jefferies analyst Andy Douglas said in a note.

Pretax profit rose to 45.1 million pounds for the six months ended June 30 from 37.1 million pounds last year, said Senior, which supplies to companies such as Rolls Royce, GE (>> General Electric Company), Boeing (>> The Boeing Company), Airbus (>> AIRBUS GROUP) and Caterpillar (>> Caterpillar Inc.).

Revenue in the Hertfordshire-based company was nearly flat at 400.4 million pounds.

The FTSE-250 company said it would pay an interim dividend of 1.67 pence per share compared with 1.52 pence last year.

Shares in the company were nearly flat at 262.1 pence in thin-volume trade at 0721 GMT (8.21 a.m. BST).

(Reporting by Aashika Jain in Bangalore; Editing by Gopakumar Warrier)