Adjusted first quarter net income and earnings per share were $21 million and $0.33 per share respectively.
Adjusted EBITDA for the first quarter was $62 million.
We generated another $103 million of operating cash flow during the first quarter and increased our net cash position to more than $210 million.
Consolidated revenue for the first quarter was $6 billion, an increase of $1.3 billion or 27% sequentially, but still well behind the pre-COVID revenue levels, which is principally driven by the year-over-year decline in volume in our aviation and marine segments when compared to 2020.
Our aviation segment volume was 1.1 billion gallons in the first quarter, essentially flat sequentially, but still well below pre-COVID activity levels.
In the U.S., we have been experiencing increased activity with TSA daily throughput back to nearly 65% of prepandemic levels.
Volume in our marine segment for the first quarter was 4.2 million metric tons, flat sequentially and down 13% from the strong prior year results we generated where the new IMO 2020 regulations were implemented last January.
Our land segment volume was 1.3 billion gallons or gallon equivalents during the first quarter, that's down 6% year-over-year, but up 2% sequentially, principally driven by increases in our World Connect natural gas operations as well as some seasonal improvement in the U.K. Land volumes have now rebounded to 97% of first quarter 2019 prepandemic levels.
Consolidated volume in the first quarter was 3.6 billion gallons, up slightly on a sequential basis, but down year-over-year, again, related to the items already mentioned.
Consolidated gross profit for the first quarter was $192 million.
That's a decrease of 18% compared to the first quarter of 2020 with an increase of $26 million or 16% sequentially.
Our aviation segment contributed $77 million of gross profit in the first quarter, down 15% year-over-year, but up 9% sequentially.
The marine segment generated first quarter gross profit of $25 million, that's down 57% year-over-year, but up 12% sequentially.
Our land segment delivered gross profit of $89 million in the first quarter, up 5% year-over-year when excluding the profitability related to the multi-service business from last year's results and actually up 24% sequentially.
Core operating expenses, which excludes bad debt expense, were $146 million in the first quarter, down $29 million or 17% from the first quarter of last year.
Looking ahead to the second quarter, operating expenses, excluding bad debt expense, should be generally in line with the first quarter in the range of $144 million to $148 million.
We had debt expenses in the first quarter with $3.6 million, down both sequentially and year-over-year and down materially from the elevated levels in the second and third quarter of 2020.
Adjusted income from operations for the first quarter was $42 million, down 38% from last year but up 68% sequentially related to the segment activity that I mentioned previously.
Adjusted EBITDA was $62 million in the first quarter, down 29% from 2020 and up 39% sequentially.
First quarter interest expense was $8.7 million, which is down 44% year-over-year and approximately 20% sequentially.
At the end of the first quarter, we again had no borrowings outstanding under our revolver and ended the quarter in a net cash position in excess of $200 million.
We expect interest expense in the second quarter to be approximately $9 million to $10 million.
Our adjusted tax rate for the first quarter was 35.8% compared to 30.6% in the first quarter of 2020.
Our total accounts receivable balance increased significantly on a sequential basis to approximately $1.7 billion at quarter end, principally related to the 37% rise in average fuel prices from the fourth quarter.
We remain focused on managing working capital requirements, which resulted in operating cash flow generation of $103 million during the first quarter despite a significant sequential increase in accounts receivable.
While we are appropriately inwardly focused over the first 12 months of the pandemic, during which time our team performed at a level of excellence for which they should all be very proud, we can now more clearly see the light at the end of the tunnel.
This strong balance sheet, including $735 million of cash, provides us with capital to further grow our core business organically as well as the ability to capitalize on strategic investment opportunities which should drive scale and efficiencies, most specifically in our land and World Connect business activities.
In demonstration of our commitment to enhancing shareholder value, over the past two years we've repurchased $134 million of our shares, and we increased our cash dividend twice, most recently, a 20% increase during the first quarter.

Summary:
Adjusted first quarter net income and earnings per share were $21 million and $0.33 per share respectively.
We expect interest expense in the second quarter to be approximately $9 million to $10 million.