<PAGE>   1




                       SECURITIES AND EXCHANGE COMMISSION

                             WASHINGTON, D.C. 20549

                                    FORM 10-Q
                QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d)


                       OF SECURITIES EXCHANGE ACT OF 1934

                  For the quarterly period ended June 30, 1999
                         Commission File Number 0-15495



                              MESA AIR GROUP, INC.
             (Exact name of registrant as specified in its charter)


                   Nevada                                       85-0302351
         (State or other jurisdiction of                      (I.R.S. Employer
          incorporation or organization)                     Identification No.)


410 North 44th Street, Suite 700, Phoenix, Arizona                 85008
    (Address of principal executive offices)                     (Zip Code)


Registrant's telephone number, including area code:            (602) 685-4000


Indicate by check mark whether the registrant (1) has filed all reports required
to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during
the preceding 12 months (or for such shorter period that the registrant was
required to file such reports), and (2) has been subject to such filing
requirements for the past 90 days.


                                Yes  x     No

On July 10, 1999 the registrant had outstanding 33,840,291 shares of Common
Stock.
<PAGE>   2
PART 1. FINANCIAL INFORMATION
Item 1.
                              MESA AIR GROUP, INC.

                 CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS
                                   (Unaudited)
                    (in thousands, except per share amounts)

<TABLE>
<CAPTION>
                                                             Three Months Ended                Nine Months Ended
                                                                   June 30                          June 30
                                                           1999             1998             1999             1998
                                                         ---------        ---------        ---------        ---------
<S>                                                      <C>              <C>              <C>              <C>
Operating revenues:

       Passenger                                         $ 103,769        $ 114,474        $ 295,395        $ 384,491
       Freight and other                                     1,504            3,117            4,792            9,948
                                                         ---------        ---------        ---------        ---------
        Total operating revenues                           105,273          117,591          300,187          394,439
                                                         ---------        ---------        ---------        ---------
Operating expenses:

         Flight operations                                  43,105           44,715          125,078          151,995
         Maintenance                                        18,038           24,282           53,640           76,693
         Aircraft and traffic servicing                     12,250           16,782           38,202           64,773
         Promotion and sales                                 8,853           16,697           24,829           56,491
         General and administrative                          6,661            7,207           19,219           24,953
         Depreciation and amortization                       4,387            6,403           13,833           21,372
         Other operating items                                  --               --              (17)          40,443
         Acquisition costs                                   3,605               --               --               --
                                                         ---------        ---------        ---------        ---------
         Total operating expenses                           96,899          116,086          274,784          436,720
                                                         ---------        ---------        ---------        ---------
         Operating income (loss)                             8,374            1,505           25,403          (42,281)
                                                         ---------        ---------        ---------        ---------
Non-operating income (expense):
         Interest expense                                   (4,475)          (5,398)         (13,455)         (18,974)
         Interest income                                       754              369            1,482            1,232
         Other                                                 129             (332)          (2,584)           4,292
                                                         ---------        ---------        ---------        ---------
         Total non-operating income (expense)               (3,592)          (5,361)         (14,557)         (13,450)
                                                         ---------        ---------        ---------        ---------
Income (Loss) before income taxes                            4,782           (3,856)          10,846          (55,731)
         Income tax benefit                                     --               --               --           (2,511)
                                                         ---------        ---------        ---------        ---------

             Net income (loss)                           $   4,782        $  (3,856)       $  10,846        $ (53,220)
                                                         =========        =========        =========        =========

Average common shares outstanding: Basic                    34,011           33,555           33,954           33,419
                                                         =========        =========        =========        =========

Average common shares outstanding: Diluted                  34,675           33,997           34,559           33,692
                                                         =========        =========        =========        =========
Net income (loss) per common and common equivalent
share, basic                                             $    0.14        $   (0.11)       $    0.32        $   (1.59)
                                                         =========        =========        =========        =========
Net income (loss) per common and common equivalent
share, diluted                                           $    0.14        $   (0.11)       $    0.31        $   (1.58)
                                                         =========        =========        =========        =========
</TABLE>



                                       2

     See accompanying notes to condensed consolidated financial statements

<PAGE>   3
                              MESA AIR GROUP, INC.

                      CONDENSED CONSOLIDATED BALANCE SHEETS
                                   (Unaudited)
                                 (in thousands)

<TABLE>
<CAPTION>
                                                                       June 30,      September 30,
                                                                         1999             1998
                                                                       --------      ------------
<S>                                                                   <C>              <C>
ASSETS
Current Assets:
    Cash and cash equivalents                                         $  56,107        $  35,667
    Receivables, primarily traffic                                       29,018           29,153
    Income tax refund receivable                                           --              9,057
    Expendable parts and supplies, net                                   28,044           30,742
    Prepaid expenses and other current assets                             9,050            6,791
                                                                      ---------        ---------
          Total current assets                                          122,219          111,410
Property and equipment, net                                             312,570          336,195
Lease and equipment deposits                                             22,712           11,515
Intangibles, net                                                         19,545           20,646
Other assets                                                              3,873            4,611
                                                                      ---------        ---------
          Total assets                                                $ 480,919        $ 484,377
                                                                      =========        =========
LIABILITIES AND STOCKHOLDERS' EQUITY
Current liabilities:
    Current portion of long-term debt                                 $  40,798        $  35,714
    Accounts payable                                                     26,346           17,784
    Air traffic liability                                                 3,932            4,758
    Accrued compensation                                                  6,730            3,834
    Other accrued expenses                                               28,491           50,828
                                                                      ---------        ---------
          Total current liabilities                                     106,297          112,918
Long-term debt excluding current portion                                233,397          243,350
Capital Lease obligations, less current obligations                       1,890            1,982
Deferred credits and other liabilities                                   17,074           16,592
                                                                      ---------        ---------
          Total liabilities                                             358,658          374,842
                                                                      ---------        ---------

Stockholders' equity:
Preferred stock of no par value, 2,000,000 shares                     $     --          $     --
authorized; no shares issued and outstanding
Common stock of no par value, 75,000,000 shares authorized;
        33,840,291 and 33,910,653 shares issued and outstanding         123,283          122,174
    Retained earnings  (deficit)                                         (1,022)         (12,639)
                                                                      ---------        ---------
          Total stockholders' equity                                    122,261          109,535
                                                                      ---------        ---------
Total liabilities and stockholders' equity                            $ 480,919        $ 484,377
                                                                      =========        =========
</TABLE>


                                       3

     See accompanying notes to condensed consolidated financial statements
<PAGE>   4
                              MESA AIR GROUP, INC.

                 CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS
                                   (Unaudited)
                                 (in thousands)

<TABLE>
<CAPTION>
                                                             Nine Months Ended June 30,
                                                                1999           1998
                                                             --------        --------
<S>                                                          <C>             <C>
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)                                            $ 10,846        $(53,220)
Adjustments to reconcile net income (loss) to
net cash flows from operating activities:
      Depreciation and amortization                            13,832          21,426
      Provision for other operating items                        --            40,443
      Amortization of deferred credits                            481         (15,433)
      Provision for doubtful accounts                              72           1,027
      (Gain)loss on sale of securities                           --            (4,544)
      (Gain)loss on sale of property and equipment              1,608             (22)
      Other                                                      --             3,022
Changes in assets and liabilities:
            Receivables                                            63          21,627
            Income tax receivable                               9,057            --
            Expendable parts and supplies                       2,698          (3,520)
            Prepaid expenses and other current assets          (2,259)         (3,826)
            Accounts payable                                    8,562           2,083
            Air traffic liability                                (826)          3,810
            Accrued compensation                                2,896          (4,552)
            Other accrued expenses                            (19,516)         (4,160)
                                                             --------        --------
             NET CASH PROVIDED BY OPERATING ACTIVITIES:        27,514           4,161
                                                             --------        --------
CASH FLOWS FROM INVESTING ACTIVITIES:
    Capital expenditures                                       (8,966)         (7,576)
    Proceeds from sale of FOUR CORNERS AVIATION                 4,500
    Proceeds from sale of property and equipment               11,703           17,659
    Proceeds from sale of marketable securities                  --            11,102
    Other assets                                                  738          (1,292)
    Lease and equipment deposits                              (11,197)         (1,430)
                                                             --------        --------
            NET CASH FLOWS FROM INVESTING ACTIVITIES           (3,222)         18,463
                                                             --------        --------
CASH FLOWS FROM FINANCING ACTIVITIES:
    Principal payments on long-term debt                       (4,961)        (34,525)
    Proceeds from issuance of common stock                      1,109           2,373
    Proceeds from deferred credits                               --             2,727
                                                             --------        --------
            NET CASH FLOWS FROM FINANCING ACTIVITIES:          (3,852)        (29,425)
                                                             --------        --------
NET CHANGE IN CASH AND CASH EQUIVALENTS:                       20,440          (6,801)

CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD               35,667          57,244
                                                             --------        --------
CASH AND CASH EQUIVALENTS AT END OF PERIOD                   $ 56,107        $ 50,443
                                                             ========        ========
</TABLE>



<TABLE>
<CAPTION>
                                                               1999            1998
                                                             --------        --------
<S>                                                          <C>             <C>
Cash paid during the nine months ended June 30 for:

     Interest                                                $  4,691        $  3,956
                                                             --------        --------
</TABLE>

     See accompanying notes to condensed consolidated financial statements

                                       4
<PAGE>   5

                              MESA AIR GROUP, INC.
              NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS

1. Basis of Presentation: The accompanying unaudited condensed consolidated
financial statements have been prepared in accordance with generally accepted
accounting principles for interim financial information and with the
instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do
not include all of the information and footnotes required by generally accepted
accounting principles for complete financial statements. In the opinion of
management, all adjustments (consisting of normal recurring accruals) considered
necessary for a fair presentation have been included. Operating results for the
three-month and nine-month periods ended June 30, 1999 are not necessarily
indicative of the results that may be expected for the fiscal year ending
September 30, 1999. These condensed consolidated financial statements should be
read in conjunction with the Company's consolidated financial statements and
footnotes included in the annual report for the fiscal year ended September 30,
1998.

2. The condensed consolidated financial statements include the accounts of Mesa
Air Group, Inc. and its wholly owned subsidiaries Mesa Airlines, Inc., WestAir
Holding, Inc., Air Midwest, Inc., CC Air, Inc., Mesa Leasing, Inc., MAGI
Insurance, Ltd., Regional Aircraft Services, Inc., The Ritz Hotel Management
Corporation, and MPD, Inc. During the quarter ended June 30, 1999, Mesa Air
Group, Inc. sold substantially all of the assets of Four Corners Aviation Inc.,
a wholly-owned subsidiary of Mesa Air Group, for its approximate book value of
$4.5 million. All significant intercompany balances and transactions have been
eliminated in consolidation. See discussion of WestAir Holding, Inc. in the
"Legal Proceedings" section of this report.

3. Income tax benefit in the nine-month period ended June 30, 1998 has been
recognized only to the extent of previously recorded deferred tax liability. For
the quarter ended June 30, 1999 and the nine-month period then ended, the
Company did not recognize any income tax expense as a result of net operating
loss carryforwards.

4. On June 9, 1999, Mesa Merger Corporation, a wholly-owned subsidiary of the
Company, merged with and into CCAIR, Inc. a regional carrier based in Charlotte,
NC, and in connection therewith the Company issued 5,743,872 shares of common
stock in exchange for all of CCAIR's outstanding common stock. CCAIR is a
regional airline serving the East Coast as US Airways Express.

The merger was accounted for as a pooling of interests and accordingly, the
companies' financial statements have been restated to include the results of
CCAIR for all periods presented.

Combined and separate results of Mesa and CCAir are as follows( in thousands):

<TABLE>
<CAPTION>
                                                  Mesa             CCAir        Adjustments.       Combined
                                               ----------        ---------      -----------        ---------
<S>                                            <C>               <C>            <C>              <C>
Quarter - ended  June 30, 1999
         Operating revenues                     $  84,109        $  21,164                         $ 105,273
         Net earnings(loss)                    ($     226)       $   5,008                         $   4,782

Quarter - ended June 30, 1998
         (CCAir as of September 30, 1998)
         Operating revenues                     $  99,523        $  18,068                         $ 117,591
         Net earnings(loss)                    ($   4,361)       $   1,098       ($    592)       ($  3,856)



Nine months - ended  June 30, 1999
         Operating revenues                     $ 239,170        $  61,017                         $ 300,187
         Net earnings(loss)                     $  10,846        $       0                         $  10,846

Nine months - ended June 30, 1998
         (CCAir as of September 30, 1998)
         Operating revenues                     $343,715         $50,725                           $ 394,439
         Net earnings(loss)                     $ 56,711         $ 3,749         ($    258)       ($ 53,220)
</TABLE>




The combined financial information contains adjustments to conform the
accounting policies of the two companies. This conforming adjustment reflects
the restatement of CCAIR's engine overhaul amounts to the direct expense method
from the accrued method for all periods. The adjustment reduced combined net
income for the three month period ended June 30, 1999 by $92,000 and increased
combined net income by $34,000 for the nine months then ended. For the three and
nine month periods ended June 30, 1998 combined net income was increased by
$230,000 and $563,000, respectively. Mesa owned 300,000 shares of common stock
in CCAIR prior to the merger, which have been accounted for as treasury shares.

The consolidated financial statements for the quarters and nine month periods
ended June 30, 1999 and 1998 respectively have not been restated to change
CCAIR's fiscal year from December 31 to September 30. They include Mesa's
results of operations on a September 30 fiscal year and CCAIR's on a calendar
year.


                                       5
<PAGE>   6
5.   Legal Proceedings:

     See, "Part II., Item 1."

This Form 10-Q contains certain statements including, but not limited to,
information regarding the replacement, deployment, and acquisition of certain
numbers and types of aircraft, and projected expenses associated therewith;
costs of compliance with FAA regulations and other rules and acts of Congress;
the passing of taxes, fuel costs, inflation, and various expenses to the
consumer; the relocation of certain operations of Mesa; the resolution of
litigation in a favorable manner; compliance with Year 2000 issues, and certain
projected financial obligations. These statements, in addition to statements
made in conjunction with the words "expect," "anticipate," "intend," "plan,"
"believe," "seek," "estimate," and similar expressions, are forward-looking
statements which we believe are within the meaning of the safe harbor provision
of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the
Securities Exchange Act of 1934, as amended. These statements relate to future
events or the future financial performance of Mesa and only reflect Management's
expectations and estimates. The following is a list of factors, among others,
that could cause actual results to differ materially from such forward-looking
statements: changing business conditions in certain market segments and
industries; an increase in competition along the routes Mesa operates or plans
to operate; material delays in completion by the manufacturer of the ordered and
yet-to-be delivered aircraft; changes in general economic conditions; changes in
fuel price; changes in regional economic conditions; Mesa's relationship with
employees and the terms of future collective bargaining agreements; and the
impact of current and future laws, Congressional investigations, and
governmental regulations affecting the airline industry and Mesa's operations;
bureaucratic delays; amendments to existing legislation; consumers unwilling to
incur greater costs for flights; unfavorable resolution of negotiations with
municipalities for the leasing of facilities; and risks associated with
litigation outcomes. One or more of these or other factors may cause Mesa's
actual results to differ materially from any forward-looking statement. Mesa is
not undertaking any obligation to update any forward-looking statements
contained in this Form 10-Q.

Item 2.

                      MANAGEMENT'S DISCUSSION AND ANALYSIS

                OF FINANCIAL CONDITION AND RESULTS OF OPERATIONS

GENERAL

Mesa Air Group, Inc. and its subsidiaries (collectively referred to as "Mesa" or
the "Company") is an independently owned regional airline serving 134 cities in
31 states, the District of Columbia, Toronto, Canada and Guaymas and Hermasillo,
Mexico. At June 30, 1999, Mesa operated a fleet of 139 aircraft with
approximately 1,000 daily departures.

On June 10, 1999 Mesa Merger Corporation, a wholly owned subsidiary of the
Company completed its merger with CCAIR, Inc., whereby CCAIR became a wholly
owned subsidiary of the Company. CCAIR is a Charlotte, North Carolina based
regional airline operating 26 aircraft as US Airways Express. The transaction,
valued at approximately $50.7 million, reflects an approximate $4.13 per share
purchase price based on a Mesa share price of $6.625 and will be accounted for
as a pooling of interests. Under the terms of the Merger Agreement, shareholders
of CCAIR received .6214 shares of Mesa common stock for each outstanding share
of CCAIR common stock.

Mesa's airline operations are conducted by three regional airlines utilizing
hub-and-spoke systems. Mesa Airlines, Inc. ("MAI"), a wholly-owned subsidiary of
Mesa, operates as America West Express under a code-sharing agreement with
America West Airlines, Inc. ("America West") and as US Airways Express under
code-sharing agreements with US Airways, Inc. ("US Airways") and also operates
an independent division, Mesa Airlines, from a hub in Albuquerque, New Mexico.
Air Midwest, Inc. and CCAIR, Inc., wholly owned subsidiaries of Mesa, also
operate under separate code-sharing agreements with US Airways and fly as US
Airways Express.

On April 2, 1999, The Ritz Hotel Management Corporation, a wholly-owned
subsidiary of the Company, purchased a motel in Mesa, Arizona for use as a
dormitory facility for its flight crews in training. The motel was purchased for
$350,000 in cash and a promissory note secured by the motel assets and executed
by the Ritz Hotel Management Corporation in the principle amount of $1,125,000
for a term of 10 years, with interest at 7% for year 1 and 7.5% thereafter.

During the past twelve months, significant changes have occurred at Mesa. In May
1998, Mesa and its WestAir subsidiary ceased all operations as United Express,
which resulted in a loss of approximately 36% of Mesa's consolidated revenue and
a flight equipment inventory with 89 excess aircraft. Mesa successfully
redeployed and disposed of almost all of the excess aircraft. In September,
1998, Mesa signed a new code-share contract with America West Airlines which
expires on August 25, 2004. In January 1998, Mesa Airlines entered into a new
code-share agreement with US Airways using Canadian Regional Jets ("CRJ")
the aircraft which expires in January 2003. In addition, Mesa has acquired an
additional 12 CRJ's since March 1998. All of the 27 regional jets which Mesa
currently operates fly under fee per departure contracts with US Airways and
America West.

Mesa's long-term business strategy is to operate a competitive and profitable,
high-frequency, quality service airline, primarily with a hub-and-spoke system.
The strategy is implemented through a disciplined approach to the regional
airline business which incorporates (i) regional diversification, (ii) focus on
profitable markets, (iii) reactions to the changing economic and competitive
environment, and (iv) a modern, efficient aircraft fleet that positions the
airline to be able to capitalize on future growth opportunities.


                                       6
<PAGE>   7
As a result of the Airline Deregulation Act of 1978, as amended, airlines in the
United States have been free to set their own domestic fares without
governmental regulation. Mesa has increasingly relied on fee per departure
contractual agreements with its two code-sharing partners to generate revenue.

All of Mesa Airlines Inc.'s America West Express operations (except Guaymas and
Hermasillo, Mexico) and US Airways Express jet operations are on a fee per
departure basis. For the quarter ended June 30, 1999, 40.1% of Mesa's airline
revenues were derived from fee per departure contractual arrangements. The
percentage of revenue generated under the fee per departure agreements is
expected to significantly increase in 1999 as Mesa adds additional regional jets
to its America West Express and US Airways Express operations. CCAIR operates on
a prorate agreement with US Airways which accounted for an additional 19.9% of
Mesa's revenue. Mesa derives the remainder of its passenger revenues from a
combination of local fares, through fares, and joint fares. Local fares are
fares for one-way and round-trip travel provided by Mesa within its route
system. Passengers connecting with other carriers also frequently use local
fares. A through-fare is a fare offered to passengers by either America West or
US Airways which generally provides cost savings to the passenger who transfers
to the major carrier's code-sharing partner on routes flown by the code-sharing
partner. Through-fares are prorated in accordance with standards specified in
the various code-sharing agreements. Joint fares are single fares for travel
combining flights with Mesa and other airlines, which are not code-sharing
partners with Mesa. With joint fares, the passenger generally pays a single
lower fare than the sum of the local fares charged for the combined flights.
Mesa has been able to negotiate joint-fare arrangements with some major carriers
as an additional means of deriving passengers connecting through its hub cities.

On May 3, 1999 Mesa Airlines, Inc. reached an agreement with the Association of
Flight Attendants (AFA), the collective bargaining representative of Mesa's
flight attendants. The contract becomes amendable on June 13, 2003. Management
does not believe the contract will have a major impact on the Company's results
of operations.




The following tables set forth year-to-year comparisons for the periods
indicated below:


                                 OPERATING DATA

<TABLE>
<CAPTION>
                                                   Three Months Ended                Nine Months Ended
                                                        June 30                            June 30
                                                  1999            1998             1999              1998
                                                  ----            ----             ----              ----
<S>                                            <C>              <C>              <C>              <C>
Passengers                                     1,104,877        1,438,408        3,142,043        4,862,627
Available seat miles (000's)                     671,958          605,396        1,895,327        1,907,628
Revenue passenger miles (000's)                  346,753          348,884          958,300        1,183,449
Load factor                                         51.6%            57.4%            50.6%            54.9%
Yield per revenue passenger mile (cents)            30.4             36.9             31.3             39.5
Revenue per available seat mile (cents)             15.7             19.4             15.8             20.7
Operating cost per
available seat mile (cents)                         13.8             19.2             14.5             22.9
Average stage length (miles)                         230              185              224              184
Number of operating aircraft in fleet                139              135              139              135
Gallons of fuel consumed                          18,237           17,724           52,080           58,737
Block hours flown                                102,751          124,526          305,758          430,976
Departures                                        91,961          123,304          278,553          426,480
</TABLE>



                                 FINANCIAL DATA
Three Months Ended June 30, 1999 Versus Three Months Ended June 30, 1998:


<TABLE>
<CAPTION>
                                                             Three Months Ended June 30
                                        --------------------------------------------------------------
                                                       1999                          1998
                                        --------------------------------------------------------------
                                     Cost per      % of total       Cost per      % of total
                                    ASM (cents)     revenues       ASM (cents)     revenues
                                 ---------------------------------------------------------------------
<S>                                 <C>            <C>             <C>            <C>
Flight operations                       6.4           41.7%            8.4           38.6%
Maintenance                             2.7           17.9%            4.2           19.4%
Aircraft and traffic servicing          1.8           12.7%            3.6           16.4%
Promotion and sales                     1.3            8.3%            3.1           14.3%
General and administrative              1.0            6.4%            1.4            6.3%
Depreciation and amortization           0.6            4.6%            1.2            5.4%
Other operating items
                                       ----           ----            ----           ----
Total operating expenses               13.8           92.7%           19.2           98.7%
Interest expense                        0.7            4.3%            1.0            4.8%
</TABLE>


                                       7
<PAGE>   8
RESULTS OF OPERATIONS

Operating Revenues:

Operating revenues decreased by $12.3 million to $105.3 million in the quarter
ended June 30, 1999, from $117.6 million in the quarter ended June 30, 1998. The
revenue decrease was primarily due to a 15.1% decrease in passengers carried.
Available seat miles ("ASMs") (capacity (# of seats) times number of miles
flown) increased by 20.9% for the quarter ended June 30,1999 over the same
period in 1998. The ASM's increased as a result of the number of CRJ's added to
the fleet which have additional seats and fly longer stage lengths as evidenced
by the increase in average stage length from 185 miles to 230 miles. The load
factor decreased from 57.4% during the quarter ended June 30, 1998 to 51.6% for
the comparable quarter in 1999. The decrease in passengers carried is primarily
attributable to the discontinuation of the Company's United Airlines Express
("United") operations. (See Part II - Item 1. Legal Events.)

Operating revenues decreased by $94.3 million to $300.2 million for the
nine-month period ended June 30, 1999 from $394.4 million for the nine-month
period ended June 30, 1998. This decrease is primarily due to the decrease in
the number of passengers carried in this period as compared to the nine months
ended June 30, 1998, as a result of Mesa's cessation of the United operations.

Operating Expenses:

As the Company's proportion of CRJ's to total aircraft increases, the operating
cost per ASM generally decreases. In addition, the fee per departure contracts
eliminate certain expenses such as commissions and reservation fees.


Flight Operations:

Flight operations costs decreased by $1.6 million to $43.1 million for the
quarter ended June 30, 1999 from the quarter ended June 30, 1998 and decreased
by $26.9 million to $125.1 million for the nine-month period ended June 30, 1999
from the nine-month period ended June 30, 1998. Flight operations expenses
decreased both quarter over quarter and for the nine-month period ended June 30,
1999. The decrease from the quarter ended June 30, 1998 to the comparable
quarter in 1999 included a $1.7 million decrease in pilot costs, a $.4 million
increase in flight attendant costs, a $1.4 million decrease in training costs,
and a $.6 million increase in aircraft leasing and ownership costs. The increase
in ownership costs and flight attendant costs reflect the reduction in Beech
1900's and the addition of CRJ jets. In the nine months ended June 30, 1999, the
cost decreases were primarily a result of the cessation of the United
operations. Ownership costs decreased in the nine months ended June 30, 1999 by
$2.0 million over the same period the previous year, pilot and training costs
decreased $14 million. Fuel cost increased $0.7 million for the quarter ended
June 30, 1999 as a result of the increase in ASM's. For the nine months ended
June 30, 1999 fuel decreased by $13.1 million over the same period the previous
year. A price reduction of approximately 2 cents per gallon over the period(s)
contributed approximately $2.7 million to the reduction.


Maintenance Expense:

Maintenance expense decreased by $6.3 million in the quarter ended June 30, 1999
to $18 million from $24.3 million in the same quarter of the previous fiscal
year and decreased by $23.1 million in the nine-month period ended June 30,
1998. The decrease for the quarter and for the nine months ended June 30, 1999
was primarily a result of the changes to the fleet composition as discussed
under "Flight Operations."

Aircraft and Traffic Service Expense:

Aircraft and traffic service expense decreased by $4.5 million to $12.3 million
during the quarter ended June 30, 1999 from $16.8 million in the comparable
quarter of the previous fiscal year. Aircraft and traffic service expense
decreased by $26.6 million to $38.2 million for the nine-month period ended June
30, 1999 from $64.8 million for the nine-month period ended June 30, 1998. The
decrease for the quarter ended June 30, 1999 included a $2.2 million reduction
in station wages, a $1.4 million reduction in rent and other station contract
services and a $0.7 million reduction in landing fees. These decreases were
primarily the result of a reduced fleet size and an increase in the fee per
departure contract flying. The expenses included under the fee per departure
category are generally "passed through" to the contracting carrier. The decrease
for the nine month period ended June 30, 1999 from the comparable period in 1998
included a $9.7 million reduction in station wages, a $7.5 million reduction in
rent and general contract services in addition to a $3.2 million decrease in
landing fees. These decreases were primarily a result of the cessation of United
Express operations.

Promotion and Sales:

Promotion and sales expense decreased $7.8 million to $8.8 million for the
quarter ended June 30, 1999 from the prior year's comparable quarter and
decreased by $31.7 million to $24.8 million for the nine-month period ended June
30, 1999 compared to the nine-month period ended June 30, 1998. The primary
reason for these decreases was a 27.6% decrease in the number of passengers
carried as a result of the cessation of United Express operations.


                                       8
<PAGE>   9
General and Administrative Expense:

General and administrative expense decreased $0.6 million for the three-month
period ended June 30, 1999 to $6.6 million as compared to the quarter ended June
30, 1998 and decreased $5.7 million to $19.2 million for the nine-month period
ended June 30, 1999, as compared to the nine-month period ended June 30, 1998.
The primary cause of the decrease for the quarter ended June 30, 1999 was a $0.4
million decrease in property, casualty and liability insurance costs in addition
to a $.3 million decrease in property taxes. The reduction of $5.7 million in
costs for the nine month period ended June 30, 1999 vs. the same period in 1998
was primarily a result of the WestAir operations cessation relating to the
termination of the United contract. Included in the decrease was a $1.8
reduction in health insurance a $2.0 million reduction in legal fees and a $1.8
million reduction in passenger insurance costs.

Depreciation and Amortization:

Depreciation and amortization decreased by $2.0 million to $4.3 million for the
quarter ended June 30, 1999 as compared to the quarter ended June 30, 1998 and
decreased $7.6 million to $13.8 million for the nine-month period ended June 30,
1999 from the comparable nine-month period in the prior year. The decrease is
attributable to aircraft fleet changes from owned Beechcraft 1900D's to leased
CRJ's.

Other Operating Items:

During the nine months ended June 30, 1998 the Company recognized a $4.0 million
loss provision related to the discontinuation of its independent jet operation
in Fort Worth, Texas. The Company also recognized $2.5 million related to
anticipated settlement costs of a shareholder class action lawsuit.
Additionally, during the same period the Company also recognized a $33.9 million
loss provision related to the discontinuation of service under the Code-Sharing
Agreements with United Airlines.

Acquisition Costs:

The Company recognized $3.6 million in merger expenses related to the
acquisition of CCAIR in the quarter ended June 30, 1999. The $3.6 million
consists of $0.6 million in legal fees, $0.3 million in accounting fees, $0.2
million in registration costs and $2.5 million in other fees.

Other Non-Operating Expense:

During the nine months ended June 30, 1998, as a result of a gain on the sale of
Mesa's investment in America West Airlines, Mesa recognized a gain of $4.5
million. Interest expense decreased by $1.0 million to $4.4 million in the
quarter ended June 30, 1999 from $5.4 million in the quarter ended June 30,
1998, due to lower outstanding principle loan balances as a result of the
retirement of aircraft. Interest expense for the nine-month period ended June
30, 1999 was reduced by $4.6 million over the comparable nine-month period in
1998 as a result of lower outstanding principle loan balances due to aircraft
fleet reductions.


LIQUIDITY AND CAPITAL RESOURCES

Mesa's cash, cash equivalents and marketable securities as of June 30, 1999 were
$56.1 million. Mesa's net cash flows from operations were approximately $27.6
million during the nine months ended June 30, 1999. Mesa makes semiannual lease
payments on a substantial portion of its leased aircraft with approximately
$15.0 million due in January and $7.0 million July. Mesa's cash, cash
equivalents and marketable securities are intended to be used for working
capital, capital expenditures and acquisitions.

Mesa had receivables of approximately $29.0 million at June 30, 1999, which
consist primarily of amounts due from code-sharing partner US Airways and
passenger ticket receivables due through the Airline Clearing House. Under the
terms of the US Airways agreement, Mesa receives a substantial portion of its
revenues through the Airline Clearing House. Historically, Mesa has generated
adequate cash flow to meet its operating needs. Termination of the United
Express code-sharing agreement has left Mesa with excess aircraft which will
need to be re-deployed on other routes, or alternatively, sold or returned to
their lessors. At June 30, 1999, Mesa had 13 excess Beech 1900D's sold and to be
delivered under various sales agreements to the purchasers by September 1999.

The Company has placed an $11.8 million refundable deposit with an aircraft
manufacturer, subject to the companies reaching an agreement.

Mesa has significant lease obligations and debt payments on existing aircraft.
At June 30, 1999, Mesa had 83 aircraft with debt balances with maturities
through December 2011. During 1996, Raytheon Aircraft Credit Corporation
("RACC") provided financing on 69 Beech 1900D aircraft. In the fall of 1998,
RACC refinanced from another lender an additional 14 Beech 1900D aircraft. The
total financing provided by RACC is secured by the aircraft and totals $261
million at June 30, 1999 with monthly payments of $2.2 million.

Future lease payments due under all aircraft leases were approximately $753
million at June 30, 1999. At June 30, 1999, 64 aircraft were leased by Mesa with
terms extending through June 2016. Total lease expense for the three months
ended June 30, 1999 was $11.6 million, and for the nine months then ended was
$32.5 million.

Mesa has ordered 32 CRJ aircraft for use in its America West Express operation
in Phoenix, Arizona and Columbus, Ohio, and for its US Airways Express
operations on the East Coast. As of June 30, 1999, Mesa had received 26 of the
32 CRJ aircraft on order and expects to take delivery of the remaining 6 by the
end of 1999. Mesa has Rolling Options for an additional 16 CRJ aircraft with a
delivery schedule subject to availability of one per month beginning June 2000.
In December 1997, Mesa gave notice to Bombardier, the manufacturer, of its
intent to exercise its option to purchase the 16 Rolling Option aircraft.
Bombardier contends that the aircraft are subject to availability and that they
are no longer available. Mesa disputes Bombardier's position. The matter has not
yet been resolved. The value of these additional 16 CRJ aircraft, at listed
prices, is approximately $320 million. Permanent financing has been completed on
15 of the 26 aircraft for which Mesa has entered into operating leases. The
manufacturer, Bombardier Regional Aircraft Division, is providing interim
financing and has agreed to provide back up financing at agreed upon rates if
Mesa is not successful in obtaining permanent


                                       9
<PAGE>   10
financing. The financing rate, but not the commitment, is subject to there being
no material adverse change in Mesa's creditworthiness. Mesa anticipates
finalizing operating leases upon the completion of permanent financing for the
additional 6 aircraft to be delivered in 1999. Mesa has negotiated 10-year
engine maintenance contracts with General Electric Aircraft Engines ("GE") for
the CRJ aircraft and with Pratt and Whitney, Canada Aircraft Services ("PWC")
for the Dash 8-200 aircraft. The GE engine maintenance contract provides
coverage for the engines on the first 16 CRJ aircraft to be delivered. Mesa is
presently negotiating with GE to add the CRJ aircraft engines for 16 additional
CRJ aircraft to this maintenance contract. The PWC contract provides coverage
for all Dash 8-200 aircraft engines operated by Mesa. Both contracts provide for
payment at the time of the repair event and a fixed dollar amount per flight
hour, subject to escalation based on changes in the Consumer Price Index, for
the number of flight hours incurred since the previous event.

In connection with the $110 million loss provision recorded of which $72.1
million was for the fiscal year ended September 30, 1997 and $37.9 million was
for the fiscal year ended September 30, 1998, Mesa incurred $3.4 million in cash
expenditures in the quarter ended June 30, 1999 and $12.6 million in cash
expenditures for the nine months then ended, primarily for the disposition of
surplus aircraft, severance and other expenditures. At June 30, 1999, Mesa had
applied $88.8 million to this provision, leaving a balance of $21.2 million for
remaining disposition costs. Management is currently reviewing remaining
disposition costs associated with the loss provision.

Management's belief that Mesa will have adequate cash flow to meet its operating
needs is a forward-looking statement. Actual cash flow could materially differ
from the forward-looking statement as a result of many factors, including; in
the event of the termination of one or more code-sharing agreements; failure to
sell, dispose of, or re-deploy excess aircraft in a timely manner; a substantial
decrease in the number of routes allocated to MAI under its code-sharing
agreement with US Airways; reduced levels of passenger revenue, additional taxes
or costs of compliance with governmental regulations, fuel cost increases,
increase in competition, increase in interest rates, general economic conditions
and unfavorable settlement of existing or potential litigation. Mesa has minimal
market risk with respect to market risk instruments such as foreign currency
exchange risk and commodity price risk. Mesa is subject to interest rate risk
with respect to current and future aircraft financings.


YEAR 2000 ISSUES

Many currently installed computer systems and software products are coded to
accept two digit entries in the date code field. These date code fields will
need to accept four digit entries to distinguish 21st century dates from 20th
century dates. Any programs that have date/time sensitive software may recognize
a date using "00" as the year 1900 rather than the year 2000. This could result
in the computer shutting down or performing incorrect computations.
Consequently, computer systems and software used by many companies will need to
be upgraded to comply with such "Year 2000" requirements. Certain of Mesa's
systems, including information and computer systems and automated equipment,
will be affected by the Year 2000 issue.

Mesa has completed a comprehensive inventory of its core business applications
to determine the adequacy of these systems to meet future business requirements.
To date, Mesa's Year 2000 assessment efforts have focused on those business
computer applications (i.e., the systems that Mesa is dependent upon for the
conduct of day-to-day business operations). Year 2000 readiness is only one of
many factors considered in this assessment. Out of this effort, a number of
systems have already been identified for upgrade or replacement. In no case has
a system been replaced or intended to be replaced solely because of Year 2000
issues, although in some cases the timing of system replacement is being
accelerated. Thus, Mesa does not believe the costs of these system replacements
are specifically Year 2000 related. Additionally, while Mesa may have incurred
an opportunity cost for addressing the Year 2000 issue, it does not believe that
any specific information technology projects have been deferred as a result of
its Year 2000 efforts.

Mesa's reservation systems are tied to its code-sharing partners, US Airways and
America West. In February, the computer reservations system (CRS) used by Mesa
and those CRS's used by each of its partners, completed a major milestone. These
systems handled the Year 2000 rollover date by successfully processing
reservations for air travel after December 31, 1999.

Mesa has installed an upgraded version of its current accounting system, which
is represented by the vendor to be Year 2000 compliant but has not yet been
tested. A new flight operations software package, which the vendor has stated to
be Year 2000 compliant, is currently being installed and tested. The
applications within this system will support crew scheduling in addition to crew
and flight tracking expected to be operational during the fourth quarter.

Mesa has had extensive discussions with the manufacturers of its various
aircraft to discuss any potential Year 2000 issues. No embedded systems in the
equipment, which have the potential to be adversely affected by the Year 2000
rollover, have been identified. The aircraft manufacturers are also required to
report the Year 2000 status of their aircraft to the FAA. Mesa currently has
three employees devoted full-time to the Year 2000 Project: two in Information
Technologies and one in the Maintenance Department.


                                       10
<PAGE>   11
Projects are currently underway to evaluate the remaining systems (including
tracking of maintenance parts, revenue accounting and payroll) and replace them
if needed, with testing and implementation scheduled for the remainder of
calendar year 1999. As with systems that have already been replaced, Mesa does
not believe that the costs of these replacements are specifically Year 2000
related. Mesa has upgraded or replaced many of its personal computers and
related system components which were not determined to be specifically related
to the Year 2000 conversion, but were part of a previously scheduled, larger
system upgrade. Mesa has spent approximately $1 million on these upgrades thus
far, and anticipates another $0.5 million in expenditures to complete its system
upgrade. Mesa expects to incur Year 2000 related costs to repair some of its
systems; these anticipated costs have been estimated at an additional $0.5
million.

Mesa is currently assessing other potential Year 2000 issues, including
non-information technology systems. The Year 2000 readiness status of Mesa's
business partners, vendors, suppliers, contractors, financial institutions and
other third parties is currently being assessed. Mesa believes that a likely
worst-case scenario for the Year 2000 issue would be if Mesa or any third
parties with which it has business relationships, would not successfully
complete their Year 2000 remediation efforts. If this were to occur, the
potential for Mesa to encounter business disruption could have a material
adverse effect on its day-to-day business operations, and therefore, its
financial position. In addition, Mesa could be materially impacted by widespread
communications or other utility outages; economic or financial market
disruption; or by computer system failures or anomalies.

Mesa has begun establishing formal Year 2000 contingency plans. Mesa maintains
and deploys contingency plans designed to address various other potential
business interruptions. These plans will address business interruptions of key
vendors and suppliers which may be affected by the Year 2000 rollover.

The Company believes that its Year 2000 project will be completed prior to any
currently anticipated significant impact on the Company arising from the Year
2000 issue.



AIRCRAFT:

The following table lists the aircraft owned and leased by Mesa for scheduled
operations as of June 30, 1999:



NUMBER OF AIRCRAFT

<TABLE>
<CAPTION>
                                                                     Operating
                                                                     On June 30,  Passenger
Type of Aircraft          Owned         Leased           Total          1999      Capacity
------------------------------------------------------------------------------------------
<S>                       <C>           <C>              <C>         <C>          <C>
Beechcraft 1900             83            10               93            75           19
Jet Stream 32               --            16               16            16           37
Dash 8-100                  --            10               10            10           37
Dash 8-200                  --            12               12            12           37
CRJ                         --            26               26            26           50
                       -----------------------------------------------------
Total                       83            74              157           139
                       -----------------------------------------------------
</TABLE>


PART II.   OTHER INFORMATION

Item 1.    Legal Proceedings

In June 1997, United Airlines filed a complaint in the United States District
Court for the Northern District of Illinois against two subsidiaries of Mesa,
Mesa Airlines, Inc. ("MAI) and WestAir Commuter Airlines, Inc. ("WestAir"),
seeking a judicial declaration of the parties' rights and obligations under two
separate written agreements, pursuant to which MAI and WestAir allegedly agreed
to provide certain airline transportation services to United including the
provision of scheduled air transportation services in certain areas of the
United States under the service mark "United Express." United contends that,
under these agreements, United has the right to "increase, decrease, or in any
other way adjust the flight frequencies, markets, or both" in certain airports
currently serviced by WestAir and/or MAI.

In January 1998, United amended its complaint to include damages related to
MAI's purported breach of contract to provide specified levels of service in
certain cities. On November 1, 1998, United filed a motion with the Court to
amend its Complaint to include an additional $4.0 million in damages resulting
from Mesa's alleged failure to remit baggage fees at Denver International
Airport to United. The motion has not yet been considered. MAI and WestAir
dispute the principal contentions in United's complaint, and unless a
satisfactory negotiated resolution is achieved, intend to defend their positions
vigorously. Furthermore, MAI and WestAir believe that United has breached its
code-sharing agreements with the respective entities and have filed a
counterclaim seeking to recover the substantial damages which have been incurred
by the business of MAI and WestAir.


                                       11
<PAGE>   12
In addition, Mesa and WestAir have filed suit against United and SkyWest
Airlines, Inc. ("SkyWest"). SkyWest was contracted to be Mesa's successor on the
West Coast. The complaint alleges that SkyWest unlawfully interfered with Mesa's
and WestAir's contracts with United. It further alleges improper conduct on the
part of United and SkyWest in terminating markets under the Mesa agreement and
leading to the non-renewal of the WestAir agreement. Mesa is seeking substantial
damages against each defendant.

In February 1999, a complaint was filed against WestAir and MAI in Superior
Court of California for Fresno County, by the former WestAir pilots, seeking
severance pay in the amount of $1.2 million plus economic and punitive damages
as a result of WestAir's termination of airline operations, following United's
non-renewal of the WestAir agreement. Mesa does not believe that the pilots will
prevail on their claims and intends to defend this matter vigorously.

Although the ultimate outcome of the above pending lawsuits cannot be determined
at this time, Mesa believes, based upon currently available information, that
the ultimate outcome of all the proceedings and claims pending against Mesa is
not expected to have a material adverse effect on Mesa's consolidated financial
position. Mesa's belief regarding the outcome of all pending proceedings and
claims is a forward-looking statement. On June 29, 1999 Lynrise Air Lease, Inc.
("Lynrise") filed suit against the Company and CCAIR in Supreme Court of the
State of New York. Lynrise was the lessor of certain Shorts model 360 aircraft
to CCAIR. In 1998, CCAIR restructured its aircraft fleet and elected to
terminate the leases held by Lynrise for the Shorts aircraft. In connection with
the early termination of the leases, CCAIR issued to Lynrise an Unsecured
Convertible Promissory Note (the "Note") in the principal amount of $8,334,770,
the Note was convertible into CCAIR stock at a price of $8.00 per share of
common stock, and as result of the merger between CCAIR and Mesa Merger
Corporation, the Note is convertible into Mesa stock at a price of $12.87 per
share of common stock. The Note is due June 30, 2004, accrues interest at the
rate of 7% per annum and requires the repayment of principal in 10 equal
semiannual installments commencing December 31, 1999 and the payment of interest
in quarterly installments commencing March 31, 1999.

The Note contains a provision that upon a change of control, Lynrise may, at its
option, require CCAIR to repurchase the Note. In its lawsuit filed against the
Company and CCAIR, Lynrise alleges that it has exercised its option to require
CCAIR to repurchase the Note after CCAIR became a wholly-owned subsidiary of the
Company on June 9, 1999. Both the Company and CCAIR contend that Lynrise waived
its rights with respect to the repurchase option and both intend to defend the
lawsuit vigorously. In addition, by letter dated August 9, 1999, Lynrise
declared that in accordance with the terms of the Note, an Event of Default had
occurred as against CCAIR for its failure to make the Repurchase Offer and
declared the principal amount of the Note and all accrued interest thereon due
and payable immediately.

Lynrise's claims against CCAIR include a claim for Declaratory Judgment that
CCAIR is obligated to repurchase the Note and a claim for breach of contract. As
against the Company, Lynrise has claimed tortious interference. Should Lynrise
prevail against CCAIR and require it to repurchase the Note, CCAIR is without
sufficient assets to repurchase the Note and would be unable to satisfy such a
judgment.

Mesa is also a party to various other legal proceedings and claims which arise
in the ordinary course of business.

Item 4.  Submission of Matters to Vote of Security Holders

At a Special Meeting of shareholders held on June 8, 1999 in Phoenix, Arizona,
the following were voted upon by the Mesa Air shareholders.

1.       The following Directors were elected:

         -     Paul R. Madden

         -     Jonathan G. Ornstein

         -     Daniel J. Altobello

         -     General Ronald R. Fogleman

         -     Jack Braly

         -     Maurice Parker

         -     James E. Swigart

         -     Herbert A. Denton

         -     Larry L. Risley

Each nominee for Director received in excess of 95% of the total votes cast.

2. The issuance of shares of Mesa Air Common Stock in accordance with the terms
of the Merger Agreement dated as of January 28, 1999, among Mesa Air Group,
Inc., Mesa Merger Corporation, and CCAIR, Inc. was approved with 15,761,537
voting for, 115,271 voting against, and 61,138 abstaining.

3. The ratification of the selection of KPMG LLP as independent auditors of the
Company for fiscal year 1999 was approved with 20,219,711 voting for, 64,466
voting against, and 115,231 abstaining.

4. The shareholder proposal to hire an investment banker to sell the Company
was not approved with 578,228 voting for, 15,148,466 voting against, and 211,252
abstaining.


                                       12
<PAGE>   13
5. The shareholder proposal to adopt Cumulative voting was not approved with
5,357,301 voting for, 9,915,839 voting against, and 4,461,462 abstaining.

Item 5.  Other Matters

      On June 8, 1999 at a meeting of the Board of Directors, Jonathan G.
Ornstein, the Company's President and Chief Executive Officer, was elected to
the position of Chairman of the Board of Directors.

      Under the terms of the Merger Agreement between Mesa Merger
Corporation, CCAIR, Inc. and Mesa Air Group, Inc. dated as of January 28, 1999,
upon closing of the transaction, CCAIR was entitled to one seat on the Mesa Air
Group Board of Directors. On June 9, 1999, the Mesa Air Group Board of Directors
appointed George Murnane, III as the CCAIR representative to the Mesa Air Board.
Mr. Murnane, 41, has served as a director of CCAIR since January 1997. Since
June 1996, Mr. Murnane has served in several Executive positions with
International Airline Support Group, Inc. including Chief Financial Officer and
Chief Operating Officer. From March 1996 to June 1996, he served as an aviation
consultant, from October 1995 to February 1996 he served as Chief Operating
Officer of Atlas Air, Inc. and from 1986 to 1995 he served as an investment
banker with Merrill Lynch & Co.



Item 6.     Exhibits and Reports on Form 8-K


(A)      Exhibits:

1.   none


(B)      Reports on Form 8-K

1.    A current report on form 8-K was filed on June 14, 1999 announcing that on
June 9, 1999 Mesa had completed the acquisition of CCAIR, Inc. pursuant to the
terms of the previously reported merger agreement dated as of January 28, 1999
by and among Mesa Air Group, Mesa Merger Corporation, and CCAIR. Pursuant to the
terms of the Merger Agreement, Mesa Merger Corporation merged with and into
CCAIR. Each share of CCAIR common stock was converted into the right to receive
0.6214 shares of Mesa Air Group common stock.


                                       13
<PAGE>   14
                                   SIGNATURES

Pursuant to the requirements of the Securities and Exchange Act of 1934, the
registrant has duly caused this report to be signed on its behalf by the
undersigned thereunto duly authorized.

                                              MESA AIR GROUP, INC.
                                              Registrant

Date:         August 13, 1999                 /s/ Michael Lotz
                                              ----------------
                                                  Michael Lotz
                                                  Chief Financial Officer
                                                 (Principal Accounting Officer)




                                       14

<PAGE>   15


                                 EXHIBIT INDEX


Number         Description

27             Financial Data Schedule