WASHINGTON — The number of people seeking U.S. jobless aid fell sharply last week, partially reversing two weeks of big gains that had raised concerns about rising layoffs.

Weekly applications for unemployment aid dropped 16,000 to 278,000, the Labor Department said Thursday. That followed a jump to 294,000 in the previous week, which was the highest level since February 2015. The four-week average, a less volatile measure, rose to 275,500.

Applications, which are a proxy for layoffs, have been below 300,000, a historically low level, for 63 straight weeks. That’s the longest such streak since 1973, when the nation’s population was smaller. That suggests companies are confident in the economy and willing to hold onto their staffs. Hiring is also typically solid when applications are so low.

Even with tepid economic growth, hiring has mostly been solid this year. The economy expanded just 0.5 percent at an annual rate from January through March, after growing only 1.4 percent at the end of last year.Signs that the economy is rebounding after its soft patch are likely to propel further job gains.