In the first quarter, systemwide RevPAR decreased 38% year-over-year and 53% versus 2019.
As we lapped the start of the U.S. lockdowns, RevPAR turned positive up more than 23% year-over-year.
Systemwide occupancy reached 55% by the end of the month driven by strong leisure demand.
In the U.S., more than 50% of adults have received at least one dose of a COVID-19 vaccine.
As a result, we're seeing a significant lift in forward bookings and occupancy, which is now around 60% as well as lengthening booking windows.
In fact, we are on pace to see record leisure demand in the U.S. over the summer months with April bookings for the summer exceeding 2019 peak levels by nearly 10%.
In the first quarter, business transient revenue was roughly 75% of 2019 levels in states that were further along in their reopening process.
Additionally, recent forecast for nonresidential fixed investment are up more than three percentage points from prior projections to 7.8%, indicating even greater optimism around business spending.
Near-term group bookings continue to be driven largely by social events and smaller group meetings, but we are seeing a slow shift back to a more normal mix of business with corporate group leads up more than 70% for future periods.
As we look out to next year, our group position is roughly 85% of peak 2019 levels with rate increases versus 2019.
In fact, last week, I was in Mexico to chair the World Travel and Tourism Council's Global Summit where more than 800 participants from all over the world attended in person and thousands more attended virtually.
During the quarter, we added 105 hotels totaling more than 16,500 rooms to our system and achieved net unit growth of 5.8%.
Overall conversions accounted for approximately 24% of additions in the quarter.
We also continued to enhance our resort footprint during the quarter with the openings of the 1,500-room Virgin Hotel Las Vegas, the Hilton Abu Dhabi Yas Island, the all-inclusive Yucatan Resort Playa del Carmen and six spectacular properties along the California Coast.
In the quarter, we signed nearly 22,000 rooms modestly ahead of our expectations.
Additionally, through our strategic partnership with Country Garden to introduce the Home2 Suites brand to China, we added more than 5,000 rooms to our pipeline.
Home2 recently celebrated its tenth anniversary, marking the milestone with nearly 1,000 rooms, hotels open and in the pipeline.
On Entrepreneur Magazine's Annual Franchise 500 List, which featured 11 of our 18 brands, Home2 was the number two hotel brand ranking only behind Hampton.
Overall, we are very happy with our development progress and excited for additional growth opportunities with more than half of our 399,000-room pipeline under construction, We're confident in our ability to grow net units in the mid-single-digit range for the next several years and continue to expect growth in the 4.5% to 5% range in 2021.
We ended the first quarter with more than 115 million Honors members, up roughly 8% year-over-year with membership increasing across every major region despite lower demand due to the pandemic.
During the quarter, systemwide RevPAR declined 38.4% versus the prior year on a comparable and currency-neutral basis as rising COVID cases and reinstated travel restrictions and lockdowns disrupted the demand environment, especially across Europe and Asia Pacific.
However, occupancy improved sequentially throughout the quarter, increasing more than 20 points.
Adjusted EBITDA was $198 million in the first quarter, down 45% year-over-year.
Management and franchise fees decreased 34%, less than RevPAR decrease as franchise fee declines were somewhat mitigated by better-than-expected license fees and development fees.
For the quarter, diluted earnings per share adjusted for special items was $0.02.
First quarter comparable U.S. RevPAR declined nearly 37% year-over-year and 50% versus 2019.
Demand improved sequentially throughout the quarter with March occupancy 62% higher than January and ending at 55%, the highest level since the pandemic began.
In the Americas outside the U.S., first quarter RevPAR declined 55% year-over-year and 63% versus 2019.
In Europe, RevPAR fell 76% year-over-year and 82% versus 2019.
In the Middle East and Africa region, RevPAR was down 32% year-over-year and 46% versus 2019.
In the Asia Pacific region, first quarter RevPAR fell 7% year-over-year and 49% versus 2019 as rising infections, lockdowns and border closures weighed on performance early in the quarter.
RevPAR in China increased 64% year-over-year with occupancy levels increasing from roughly 35% to roughly 65% during the quarter.
As Chris mentioned, in the first quarter, we grew net units 5.8% driven primarily by the Americas and Asia Pacific.
For the full year, we continue to expect net unit growth of 4.5% to 5%.
We repaid $500 million of the outstanding balance under our $1.75 billion revolving credit facility and opportunistically executed a favorable debt refinancing transaction to extend our maturities at lower rates.

Summary:
During the quarter, systemwide RevPAR declined 38.4% versus the prior year on a comparable and currency-neutral basis as rising COVID cases and reinstated travel restrictions and lockdowns disrupted the demand environment, especially across Europe and Asia Pacific.
For the quarter, diluted earnings per share adjusted for special items was $0.02.