Chicago Mayor Brandon Johnson will seek approval from aldermen to sell as much as $4.3 billion of debt for O’Hare International Airport, according to a filing posted on the city clerk’s website.

If authorized, proceeds of the bonds will fund infrastructure projects at the facility, as well as refinance outstanding obligations, the ordinance that the mayor is scheduled to propose Wednesday said.

O’Hare is in the midst of a massive modernization plan that seeks to transform the aging hub into a global showcase. It includes a new terminal and the expansion of existing spaces. Last year, United Airlines Holdings Inc. and American Airlines Group Inc. have reached an agreement to press ahead with the development plans.

In addition to the debt for O’Hare, Johnson is also expected to request the issuance of $265 million of debt for Chicago Midway International Airport, according to the filing. Both deals would be senior lien revenue bonds.

The bonds may be issued with either fixed or variable rates and they could be taxable or tax-exempt. The longest maturity date is capped at Jan. 1, 2066, according to the filing.

After the ordinance is introduced, it will be assigned to a committee and if approved would be considered by the full City Council. The city declined to offer further comment.

Separately, S&P Global Ratings on Tuesday assigned a BBB rating to the city’s upcoming general obligation bonds worth about $517.9 million.