LOT Polish Airlines expects to bring its two grounded Boeing 787s back into service by mid-June.

LOT, which was the first European airline to take delivery of the 787, has had one aircraft stranded in Chicago and one in Warsaw since Jan. 16 when FAA grounded the aircraft due to lithium ion battery issues.

Boeing said Wednesday it has started FAA-approved 787 battery system modifications on 10 in-service fleet aircraft, which it hopes to complete on nearly all 50 in-service fleet aircraft by mid-May. The manufacturer has also begun installing modifications on nine production aircraft and is on track to resume new 787 deliveries by early- to mid-May.

LOT is expecting delivery of its third aircraft in June or July; its third aircraft had been used by Boeing for test flights.

The carrier will need six to eight weeks to get its 787 back in service, The Wall Street Journal is reporting. The airline will send its two 787s to a certified maintenance facility in Addis Ababa, Ethiopia for retrofitting, which takes about 10 days. Ethiopian Airlines is also a 787 operator.

According to WSJ, LOT will restart 787 pilot training in mid-May and hopes by early June to have enough pilots ready to operate the aircraft.

The airline estimates it has lost several dozen million zlotys due to the grounding, but also fears some damage to its brand, several media outlets have quoted a LOT spokesman as saying.

LOT is also facing financial difficulties and deep restructuring measures as it struggles to survive.

LOT is leasing additional aircraft to make up the capacity of its long-haul fleet due to the 787 grounding.