-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
Originator-Key-Asymmetric:
 MFgwCgYEVQgBAQICAf8DSgAwRwJAW2sNKK9AVtBzYZmr6aGjlWyK3XmZv3dTINen
 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 DeF9ZfXHihI684aAdQmwYXlmuaj6AS6beoLRUM3Y7L3NsCDCEBAeQj5qhshBj+04
 wfd8/fpDP3y0xBoHh48xrA==

<SEC-DOCUMENT>0001185849-05-000025.txt : 20050923
<SEC-HEADER>0001185849-05-000025.hdr.sgml : 20050923
<ACCEPTANCE-DATETIME>20050923173810
ACCESSION NUMBER:		0001185849-05-000025
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20050908
FILED AS OF DATE:		20050923
DATE AS OF CHANGE:		20050923

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			FRONTIER AIRLINES INC /CO/
		CENTRAL INDEX KEY:			0000921929
		STANDARD INDUSTRIAL CLASSIFICATION:	AIR TRANSPORTATION, SCHEDULED [4512]
		IRS NUMBER:				841256945
		STATE OF INCORPORATION:			CO
		FISCAL YEAR END:			0331

	BUSINESS ADDRESS:	
		STREET 1:		7001 TOWER ROAD
		CITY:			DENVER
		STATE:			CO
		ZIP:			80249
		BUSINESS PHONE:		7203744200

	MAIL ADDRESS:	
		STREET 1:		7001 TOWER ROAD
		CITY:			DENVER
		STATE:			CO
		ZIP:			80249

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			UPCHURCH JAMES B
		CENTRAL INDEX KEY:			0001251879

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-12805
		FILM NUMBER:		051101370

	BUSINESS ADDRESS:	
		STREET 1:		C/O FRONTIER AIRLINES
		STREET 2:		7001 TOWER ROAD
		CITY:			DENVER
		STATE:			CO
		ZIP:			80249-7312
		BUSINESS PHONE:		7203744512
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2005-09-08</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000921929</issuerCik>
        <issuerName>FRONTIER AIRLINES INC /CO/</issuerName>
        <issuerTradingSymbol>FRNT</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001251879</rptOwnerCik>
            <rptOwnerName>UPCHURCH JAMES B</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>FRONTIER AIRLINES, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>7001 TOWER ROAD</rptOwnerStreet2>
            <rptOwnerCity>DENVER</rptOwnerCity>
            <rptOwnerState>CO</rptOwnerState>
            <rptOwnerZipCode>80249</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Restricted Stock Units</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>0</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2005-09-08</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>2000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2008-09-08</value>
            </exerciseDate>
            <expirationDate>
                <value>2008-09-08</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>2000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <ownerSignature>
        <signatureName>David Sislowski, Attorney-in-Fact</signatureName>
        <signatureDate>2005-09-23</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
-----END PRIVACY-ENHANCED MESSAGE-----