Howmet Aerospace (HWM) 10-Q 2006 Q1 Quarterly report

EXHIBIT 15

April 26, 2006

Securities and Exchange Commission

100 F Street, NE

Washington, D.C. 20549

RE: Alcoa Inc.

Commissioners:

We are aware that our report dated April 26, 2006, on our review of interim financial information of Alcoa Inc. and its subsidiaries (Alcoa) for the three-month periods ended March 31, 2006 and 2005 and included in Alcoa’s quarterly report on Form 10-Q for the quarter ended March 31, 2006 is incorporated by reference in its Registration Statements on Form S-8 (Nos. 33-24846, 333-32516, 333-106411, 33-22346, 33-49109, 33-60305, 333-27903, 333-62663, 333-79575, 333-36208, 333-37740, 333-39708, 333-115717, and 333-128445) and Form S-3 (No. 333-74874).

Very truly yours,

/s/ PricewaterhouseCoopers LLP

Pittsburgh, Pennsylvania

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