Delta Air posted a bigger-than-expected loss for the first quarter on Thursday, while also forecasting a return to profitability later this year as more people get vaccinated and start traveling again.

Air travel, stifled by the COVID-19 pandemic, is widely expected to rebound in the second half of 2021 as wide vaccine rollouts encourage travel and drive summer bookings.

"A year after the onset of the pandemic, travelers are gaining confidence and beginning to reclaim their lives," Delta Chief Executive Officer Ed Bastian said in a statement.

Delta also expects positive cash generation for the quarter ending June. It expects adjusted revenue for the period to fall between 50% and 55% from two years ago, but the drop would be less than the over 60% decline in the first quarter.

The carrier's June-quarter adjusted revenue came in at $12.5 billion in 2019, which translates to at least about $5.62 billion in the same period this year, according to Reuters calculations.

Analysts on average expect revenue of $6.22 billion for the June quarter, according to IBES data from Refinitiv.

The carrier said its move to stop blocking middle seats on May 1 could result in a sequential improvement in revenue.

The Atlanta-based company anticipates getting about $2.7 billion in the second quarter from the US Treasury under its payroll support program.

Delta said its average daily cash burn slowed to $11 million per day in the first quarter ended March 31 from $12 million per day in the previous quarter.

Total operating revenue fell 60.4% to $4.15 billion compared with the same period in 2019, and adjusted net loss was $2.26 billion, or $3.55 per share.

Analysts on average had estimated a loss of $3.17 per share on revenue of $3.91 billion.

Delta said its June-quarter adjusted pre-tax loss is expected to narrow to between $1 billion and $1.5 billion.