In a $30 billion deal, Aon is buying Willis Towers Watson, a rival in business insurance and risk consulting, but it raises one question in the mind of most Chicagoans: What will happen to the Willis Tower name now that we’ve gotten used to calling it that?

The deal between the two London-based companies was announced Monday. Executives said the combined operation will use the Aon name, not Willis.

As for the name on Chicago’s 110-story tower, Aon wouldn’t comment. A Willis Tower Watson spokesman did not reply to an email. An executive at Willis Tower — that’s the building, not the insurance company — wouldn’t comment, said a spokesman.

The former Sears Tower was rechristened in 2009 in a move that outraged some Chicagoans and even tenants of the building. The naming rights deal, arranged by what was then called Willis Group Holdings, reportedly expires in 2025.

Over the years, a tenant-friendly building modernization and a reworking of its Skydeck have ingrained the Willis Tower name in some minds.

Aon already has its name attached to the Aon Center, the former Standard Oil Building at 200 E. Randolph. With substantial offices still in Chicago, Aon will temporarily account for the names on two Chicago buildings.

But with the Willis name disappearing, that’s unlikely to continue. It’s possible that one of the tower’s marquee tenants, United Airlines Holdings, will bid for the naming rights.

The sale will give Willis Tower Watson owners 1.08 Aon shares for each of their Willis shares, representing a roughly 16% premium over the stock’s closing price on Friday. The sale could close in early 2021 but shareholders must approve it first.

During Monday’s market crash, Aon shares fell $35.88 to $178.93 and Willis shares tumbled $14.97 to $184.74.

Aon CEO Greg Case will run the combined company.