SCHEDULE 13G

Item 1(a).

Name of Issuer:

Ameristar Casinos, Inc.

Item 1(b).

Address of Issuer's Principal Executive Offices:

3773 Howard Hughes Parkway

Suite 490 South

Las Vegas, Nevada 89169

Item 2(a).

Name and Background of Person(s) Filing:

PAR Investment Partners, L.P

PAR Group, L.P.

PAR Capital Management, Inc.

Item 2(b).

Business Mailing Address for the Person Filing:

PAR Capital Management, Inc.

One International Place, Suite 2401

Boston, MA 02110

Item 2(c).

Citizenship:

State of Delaware

Item 2(d).

Title of Class of Securities:

Common stock, par value $.01

Item 2(e).

CUSIP Number:

03070Q101

Item 3.

If this statement is filed pursuant to Rules 13d-1(b), or 13d-2(b), check whether the person filing is a:

Not Applicable

Item 4.

Ownership:

(a)  Amount Beneficially Owned:

3,189,538 common stock, par value $.01

(b)  Percent of Class:

9.9% common stock, par value $.01

(c)  Number of shares as to which such person has:

(i)

sole power to vote or to direct the vote:

3,189,538 common stock, par value $.01

(ii)

shared power to vote or to direct the vote:

(iii)

sole power to dispose or to direct the disposition of:

3,189,538 common stock, par value $.01

(iv)

shared power to dispose or to direct the disposition of:

On April 19, 2011, the issuer completed a repurchase of 26,150,000 shares of its common stock. This transaction reduced the issuer’s shares outstanding by approximately 45%. As a result, the percentage ownership of the issuer’s common stock by the reporting persons increased proportionately. The reporting persons are making this filing to reflect their ownership of the issuer’s common stock as a result of the repurchase, not as a result of acquisitions of the issuer’s common stock.

Item 5.

Ownership of Five Percent or Less of a Class:

Not Applicable

Item 6.

Ownership of More than Five Percent on Behalf of Another Person:

Not Applicable

Item 7.

Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on By the Parent Holding Company:

Not Applicable

Item 8.

Identification and Classification of Members of the Group:

Not Applicable

Item 9.

Notice of Dissolution of Group:

Not Applicable

Item 10.

Certification:

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect.