The facility can be converted into 29.9% of the entire issued share capital of London Southend Airport Company Ltd, a subsidiary of Esken.
The transaction will provide funding of GBP100mln after GBP20mln will be ring-fenced to support London Southend Airport (LSA) for three years.
Esken said it will use it to repay the outstanding amounts payable under an existing facility that totalled GBP95mln as of 30 June.
It added that the agreement would reduce its overall bank debt, allow it to meet certain of its residual legacy obligations and underpin the business plan for the group.
The firm said CGI brings expertise in investing in and developing airports around the world, which will enhance its offering.
“CGI represents a true strategic development partner that will enable us to realise the full potential of LSA. Carlyle is a global investment firm with US$260bn under management,” said David Shearer, executive chairman at Esken.
“The combination of the proven operational capability of the LSA management along with the airport development experience of CGI and its financial strength will provide a strong platform as we rebuild our commercial relationships with our airline and other partners into the recovery.”