ClassPass built its business on helping people book exercise classes at local gyms. So when the pandemic forced gyms across the United States to close, the company shifted to virtual classes.

Then ClassPass received a concerning message from Apple. Because the classes it sold on its iPhone app were now virtual, Apple said it was entitled to 30 percent of the sales, up from no fee previously, according to a person close to ClassPass who spoke on the condition of anonymity for fear of upsetting Apple. The iPhone maker said it was merely enforcing a decade-old rule.

Airbnb experienced similar demands from Apple after it began an “online experiences” business that offered virtual cooking classes, meditation sessions and drag-queen shows, augmenting the in-person experiences it started selling in 2016, according to two people familiar with the issues.

Airbnb discussed Apple’s demands with House lawmakers’ offices that are investigating how Apple controls its App Store, according to three people who spoke on the condition of anonymity to discuss private conversations. Those lawmakers are now considering Apple’s efforts to collect a commission from Airbnb and ClassPass as part of their yearlong antitrust inquiry into the biggest tech companies, according to a person with knowledge of their investigat

Those lawmakers are set to grill Tim Cook, Apple’s chief executive, and the chief executives of Amazon, Facebook and Google in a high-profile hearing on Wednesday.

Apple’s disputes with the smaller companies point to the control the world’s largest tech companies have had over the shift to online life brought on by the pandemic. While much of the rest of the economy is struggling, the pandemic has further entrenched their businesses.

With millions more employees working from home, Amazon and Google are selling more online cloud space, with revenue for Amazon Web Services and Google Cloud soaring in the first quarter of the year, which included the start of the pandemic. Facebook and YouTube, which is part of Google, some of the internet’s largest gathering places, had traffic surge as people couldn’t socialize in person.

Apple has also brought in more revenue from its online-services business, mostly on the back of its App Store, and its Macs, iPads and iPhones have become even more important tools.

With gyms shut down, ClassPass dropped its typical commission on virtual classes, passing along 100 percent of sales to gyms, the person close to the company said. That meant Apple would have taken its cut from hundreds of struggling independent fitness centers, yoga studios and boxing gyms.

Apple said that with Airbnb and ClassPass, it was not trying to generate revenue — though that is a side effect — but instead was trying to enforce a rule that has been in place since it first published its app guidelines in 2010.