WHITE PLAINS, N.Y. — Hillary Clinton returned to the campaign trail Thursday, smiling and chatting with reporters as her plane flew to North Carolina. The Democratic presidential candidate appeared energetic and in high spirits after the bout of pneumonia that sidelined her.

She said she was “doing great” and “excited to get to North Carolina.” She was expected to take more extensive questions later Thursday.

Clinton left a 9/11 memorial service in New York on Sunday, stumbling and being supported by others as she entered her car. Her campaign said later that she had been diagnosed with mild pneumonia on Friday. That episode has brought new attention to the candidates’ health and raised questions about her openness and Donald Trump’s on the subject.

“I’m really glad that I did finally follow my doctor’s orders and take some days to rest instead of just trying to keep powering through, which I think is a common experience for people,” Clinton told the “Tom Joyner Morning Show” in an interview broadcast Thursday morning.

Clinton and Trump both released letters from their doctors this week with additional details about their health, including their cholesterol levels, blood pressure and current medications. Both candidates’ physicians declared them fit to serve as president.

In releasing a letter from Trump’s doctor Thursday, Trump’s team appeared to take a swipe at Clinton’s brief absence from the campaign trail.

“We are pleased to disclose all of the test results which show that Mr. Trump is in excellent health, and has the stamina to endure – uninterrupted – the rigors of a punishing and unprecedented presidential campaign and, more importantly, the singularly demanding job of president of the United States,” the campaign said in statement.

Trump first provided a summary of a recent physical to Dr. Mehmet Oz while taping an episode of Oz’s TV show. He said on the show that he gets exercise during the campaign by delivering speeches at rallies, calling them “a lot of work” and requiring “a lot of motion.”

Until now, the main source of information about Trump’s health has been a widely mocked letter from his longtime physician declaring he would be the healthiest president in history. Clinton released information from her doctor more than a year ago and provided updated information Wednesday following her pneumonia diagnosis.

The Clinton campaign’s handling of her pneumonia underscored her penchant for privacy, something that has contributed to the public’s lack of trust in the former secretary of state. Less than two months from Election Day, that has contributed to a race that is tighter than many expected.

Clinton was campaigning Thursday in Greensboro, North Carolina, and speaking to a Hispanic group in Washington. Those are her first public appearance since Sunday, when she abruptly left a 9/11 memorial service in New York after becoming dizzy and dehydrated.

Jennifer Palmieri, Clinton’s communications director, said the candidate’s break from the campaign trail helped her “sharpen the final argument she will present to voters in these closing weeks.” Clinton’s remarks Thursday were to focus on lifting up children and families, as the campaign tries to break through with a more positive message.

Meanwhile on Thursday, Trump delivered a speech in New York in which he vowed to boost the nation’s economy by at least 3.5 percent — well above current projections — and create 25 million new jobs over a decade.

The heart of his plan is a revised tax code, which includes a pledge that no business should pay more than 15 percent of its income in taxes, a major drop from the current 35 percent highest corporate tax rate. He also is proposing a simplified individuals’ tax code, reducing the current seven tax brackets, to three: 12 percent, 25 percent and 33 percent of income after deductions.

He said Thursday he would cut the number of regulations imposed by the federal government, including some of those that currently are intended to protect the food Americans eat and the air they breathe

The new letter from Clinton’s doctor stated that a chest scan revealed she had “mild, non-contagious bacterial pneumonia.” Dr. Lisa Bardack, chair of internal medicine at CareMount Medical in Mount Kisco, New York, said Clinton was treated with a 10-day course of Levaquin, an antibiotic used to treat infections.

“She is recovering well with antibiotics and rest,” wrote Bardack, who also authored a letter about Clinton’s health released in July 2015. “She continues to remain healthy and fit to serve as president of the United States.”

Clinton, 68, has blood pressure of 100 over 70. Her total cholesterol was 189; her LDL or “bad” cholesterol was 103, and her HDL or “good” cholesterol was 56 – all within healthy levels and not signaling the need for any medication. She has also had a normal mammogram and breast ultrasound, according to the letter.

The letter from Clinton’s doctor made no mention of her weight, a key part of any medical exam, nor did a similar letter released last year.

Trump’s doctor says the Republican is 6-foot-3 and 236 pounds – giving him a body mass index falling into the “overweight” range. The 70-year-old has blood pressure of 116 over 70 and his total cholesterol is 169, his doctor says.

Clinton running mate Tim Kaine also released a letter from his doctor, Brian Monahan, the attending physician of Congress. The letter says Kaine is in “overall excellent health,” has never smoked and has “modest” alcohol use.

Trump’s running mate Mike Pence said he plans to release records from a recent physical examination Thursday.

Associated Press Chief Medical Writer Marilynn Marchione in Milwaukee, AP writers Jonathan Lemire and Scott Bauer in New York and Jill Colvin in Washington contributed to this report.