Etihad Airways plans to cut 50 pilot jobs by end of this month after a significant loss last year, two sources who have seen an internal memo by the airline told Reuters on Thursday.

The state-owned Gulf carrier has been reviewing its business since 2016 after a strategy of investing billions of dollars in other airlines failed.

Etihad has around 160 surplus pilots and will lay off 50 by the end of January, the airline told pilots in the memo, according to the sources, who declined to be named because the memo was intended to be private.

The Abu Dhabi-based carrier employs 2,065 pilots, the sources added.

An Etihad spokeswoman told Reuters its flight operations department was under review and that any reduction in staff was likely to be small.

The airline also said in the memo it made a "significant loss" last year and that this would continue into 2019.

Etihad is yet to report its financial results for 2018

Chief Executive Tony Douglas told Reuters in July the airline was becoming "more rational" after racking up around $3.5 billion in losses in the previous two years.

Etihad, which once had plans to rival Emirates and Qatar Airways, is now focusing on point-to-point routes after cutting flights it said were not sustainable.

The airline plans to cut operating costs by 7 to 10 percent across its network and focus on efficiencies across the organization, the sources said.

Last year, Etihad encouraged pilots to take unpaid leave for periods ranging from as little as one week to as long as 18 months as it reviewed its fleet requirements with the intention of retiring some aircraft, sources previously told Reuters.

It also has an agreement for Emirates to take some of its surplus pilots on a temporary basis. Few pilots have taken up the offer, sources said.