The chief executive of Translink has been criticised for not appearing before Stormont's regional development committee.
On Wednesday, the committee discussed the issue of Translink's offer of a pay rise of 24% to its train drivers.
Committee chairman Jimmy Spratt said he did not think it was "a hardship for someone on £200,000" to appear before it and "explain what's going on".
MLAs were told Catherine Mason was honouring a family commitment.
The explanation was given by the chief operating officer of Translink, Philip O'Neill, who stood in for her at the meeting.
SDLP assembly member John Dallat said he was disappointed at Ms Mason's non-appearance, and added that he could have been meeting the prime minister on Wednesday.
"Anyone who puts a family commitment before appearing at this committee needs to consider their position," he added.
Translink's next three-year plan has revealed the company expects to move into the red after this year. It has also announced that fares will go up by an average of 3%.
It is anticipated that Translink will make a profit of £2m this year (2012-2013) but will then start to make significant losses with a deficit of £11.6m expected in 2013-2014, and £10.5m the following year (2014-15).
These losses are expected even after assuming the Department for Regional Development would provide additional in-year funding for rail services of £5m and £10m in the respective loss-making years.
Ciaran Doran from the Department for Regional Development said the offer to the train drivers had to be put in the context of 20 new trains being introduced to Northern Ireland in the next year, which would include an improved timetable.
Mr O'Neill said the pay offer was in association with changes to drivers' terms and conditions which would offer greater flexibility in terms of their rosters.
"In return for more pay, drivers will be doing more," he added.
Mr O'Neill said that he was confident about Translink's business case for the pay offer and that it could fund it.
However, Independent MLA David McNarry said Translink should be wary of assuming the pay offer would get "royal assent" or that the committee would "unanimously endorse" it.