The debt owed by Prestwick Airport to the Scottish government has risen in the past year from £30m to £38.4m.
That was while revenue rose through a doubling of funds from refuelling aircraft at the publicly-owned facility.
Accounts lodged with Companies House show the holding company made a loss of £7.6m in the year to March, down from £8.6m the previous year.
Revenue was up on the year from £13.6m to £18.2m.
That included a £3m extra contribution from refuelling, and a rise of £300,000 in cargo earnings, reaching £2.8m.
The debt reflects recent years of losses that have built up since the Ayrshire airport was saved from closure by a Scottish government takeover.
Under new leadership during the last financial year, there has been an effort to win new routes operating out of Prestwick, with business development activity and incentives through lowered landing fees.
But it has resulted in only one additional route linking with Poland.
The strategic report, filed with the accounts on 31 December, says that Brexit uncertainty has contributed to the difficulty of expanding the route network beyond Ryanair's few flights.
It also says the Air Departure Tax level is a further deterrent.
The Scottish government has said it intends to halve that, having taken on the powers to adjust it, but it remains at the same levels set by Whitehall.
Directors say that management began a new effort to boost income and lower costs towards the end of last financial year, and that it should show better results in the next set of accounts.
Prestwick Airport is seen as a strategic economic asset, particularly for Ayrshire, which Scottish ministers want to see returned to the private sector once it has become profitable.
It employs 315 staff, 280 of them operational, with a payroll bill of £9.4m.
The accounts state that the top-paid director earns £126,000, down from £164,000 paid out in 2016-17.