Aviation-services supplier AAR agreed to buy a 65% interest in privately held aircraft-maintenance company MRO Holdings for $1.8 billion, according to people familiar with the matter. Wood Dale, Ill.-based AAR would have the option to buy the rest of MRO within six years of the deal’s closing. AAR, founded in 1955, has a market value of around $4.7 billion as of Monday.

MRO performs aircraft maintenance and modifications at facilities in the U.S., as well as in Mexico, El Salvador and Colombia. Roughly 90% of MRO’s revenue comes from sales to U.S. customers, largely airlines. Bain Capital took a minority stake in MRO in 2024, joining founder Roberto Kriete’s family and Caoba Capital as co-owners.

As part of the new deal, Bain would retain a stake in MRO and gain a stake in AAR. AAR would issue about $780 million in new AAR stock to MRO’s investors, including Bain. AAR expects to reach Ebitda margins of 19% to 20% within three to four years following the deal, up from the 13% to 14% range for AAR’s margins now.