Full-year traffic rose just 4pc to 149 million passengers as a result.
For the year ended March 31, post-tax profit before exceptional items is set to be at the lower end of the guidance range between EUR950 million and EUR1.00 billion, compared to EUR1.02 billion the year before.
In March, Ryanair Group handled a total of 5.7 million passengers, down 47.7 percent compared with the 10.9 million passengers handled by the group in the same month of past year, the airline said in a statement.
For March alone, when the restrictions were first imposed, the group's passenger numbers plunged 48% year-on-year to 5.7 million from 10.9 million.
The firm said it was still on track to carry 154 million travellers in early March before the coronavirus pandemic hit.
The airline expects its fleet to remain largely grounded for at least April and May. We therefore expect to record ineffectiveness on our full-year 2021 fuel hedges as an exceptional item in our 2020 results.
These include grounding craft, deferring capital expenditure, suspending share buybacks, freezing recruitment and discretionary spending, and cutting all pay, including for senior management, by 50% for April and May. It is now operating fewer than 20 daily flights, or less than 1% of its normal schedule of more than 2,500 flights. It added that it supports "the EU Commission's position that any such government [financial] supports must comply with all EU state aid and competition rules".
While many airlines in the United Kingdom and Europe have asked for - or are in talks for - government bailouts, Ryanair's chief executive Michael O'Leary claimed his carrier could survive on its cash without any flights or revenue for up to a year.
Ryanair has been forced to park a lot of its fleet.
This included a number of rescue and medical flights on behalf of various European Union governments.