Sydney Airport Holdings Pty Ltd on Monday rejected an improved A$22.80 billion ($16.81 billion) bid from a group of infrastructure investors, saying that it undervalued the airport operator, but that it was open to a higher offer, Reuters reported. The new offer valued Sydney Airport at A$8.45 per share, 2.4% higher than the previous offer of A$8.25 a share, and a more than 9% premium to the stock's Friday close. A successful takeover would be among the largest buyouts ever of an Australian firm and underline a year of stellar deal activity, that has already seen a mega $29 billion buyout of Afterpay by Square. But it would require Sydney Airport to allow due diligence as well as receiving approvals from shareholders, the competition regulator and the Foreign Investment Review Board, a process that typically takes months. The unanimous board rejection comes a month after the airport operator turned down an initial bid from the Sydney Aviation Alliance (SAA), a consortium of Australian investors IFM Investors and QSuper and U.S.-based Global Infrastructure Partners. Read more.