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                                                                     Exhibit 5.2

               [ON LETTERHEAD OF CASSELS BROCK & BLACKWELL LLP]



September 18, 2000



TRAVELBYUS COM LTD.
204-3237 King George Highway
South Surrey, British Columbia
V4P 1B7

Dear Sirs:

Re:     Registration Statement on Form S-4 (File No. 333-40352)

We refer to the Form S-4 Registration Statement of Aviation Group, Inc., a
corporation incorporated pursuant to the laws of Texas ("Aviation"), filed with
the Securities and Exchange Commission (the "SEC") and the Joint Proxy
Statement/Prospectus and Prospectus Supplement contained therein (the
"Registration Statement"), for the purpose of registering under the Securities
Act of 1933, as amended (the "Act"), a certain number of shares of Aviation's
common stock, $0.01 par value per share and a certain number of shares of
Aviation's Series C convertible preferred stock, $0.01 par value. The
exchangeable shares (the "Exchangeable Shares") are to be issued in exchange for
all of the issued and outstanding common shares (the "Travelbyus Common Shares")
in the capital of travelbyus.com ltd., a corporation incorporated pursuant to
the laws of the Province of Ontario ("Travelbyus"). The Exchangeable Shares are
to be issued in connection with a proposed arrangement to be completed pursuant
to the provisions of the Business Corporations Act, Ontario (the "Arrangement")
and the Arrangement Agreement and Plan of Arrangement, dated as of May 3, 2000
(the "Arrangement Agreement") among Travelbyus, Aviation and Aviation's
wholly-owned subsidiary, Aviation Group Canada Ltd.

The issuance of the Exchangeable Shares is dependent upon the approval by the
requisite number of shareholders of Travelbyus of the Arrangement and the
Arrangement Agreement, including without limitation, the approval of an
amendment to the articles of incorporation of Travelbyus (the "Amendment")
authorizing and approving, among other things, the creation of the Exchangeable
Shares and the conversion of the issued and outstanding Travelbyus Common Shares
in to the Exchangeable Shares. The creation of the Exchangeable Shares and the
conversion of the issued and outstanding Travelbyus
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Common Shares into the Exchangeable Shares is also subject to requisite
regulatory approval, including without limitation, the approval of The Toronto
Stock Exchange (the "TSE").

We have examined originals or copies, certified or identified to our
satisfaction, of the constating documents and by-laws of Travelbyus and of such
corporate records of Travelbyus, certificates of public officials, officers of
Travelbyus and such other documents and we have considered such questions of law
and we have made such other investigations as we have deemed relevant or
necessary as a basis for the opinions hereinafter expressed.

We have assumed the genuineness of all signatures, the authenticity of all
documents submitted to us as originals and the conformity to authentic original
documents of all documents submitted to us as certified, conformed or
photostatic copies of facsimiles thereof and the authenticity of originals of
such certified, conformed or photostatic copies of facsimiles. We have also
considered such questions of law as we have deemed relevant and necessary as a
basis for the opinions set forth below.

We are solicitors qualified to carry on the practice of law in the Province of
Ontario and we express no opinion as to any laws or matters governed by any
laws, other than the laws of the Province of Ontario and the federal laws of
Canada applicable therein. The opinions herein are limited to the laws of the
Province of Ontario in effect as of the date hereof and we assume no obligation
to update these opinions to take into account any changes in such laws after the
date hereof.

Based upon and subject to the foregoing, we are of the opinion that:

1.      Assuming that both the Arrangement and the Amendment are properly
        approved and effected by the requisite number of shareholders of
        Travelbyus as set forth in the Registration Statement, all necessary
        corporate action on the part of Travelbyus will have been taken to
        authorize the issuance of the Exchangeable Shares in exchange for the
        Travelbyus Common Shares.

2.      Assuming that both the Arrangement and the Amendment are properly
        approved and effected by the requisite number of shareholders of
        Travelbyus as set forth in the Registration Statement and that
        Travelbyus receives all requisite regulatory approvals in connection
        therewith, including without limitation, the approval of the TSE, if, as
        and when the Exchangeable Shares are issued and delivered by Travelbyus
        in accordance with their terms and as contemplated by the Registration
        Statement, the Exchangeable Shares will be duly issued as fully paid,
        and non-assessable shares.
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We hereby consent to the reference to our firm in the Joint Proxy
Statement/Prospectus and the Prospectus Supplement, which constitute a part of
the Registration Statement referred to above. In giving our consent, we do not
thereby admit that we are in the category of persons whose consent is required
under Section 7 of the Act or the rules and regulations of the Securities and
Exchange Commission thereunder.

This opinion has been delivered to you solely for the purpose of being included
as an exhibit to the Registration Statement. It may not be relied upon for any
other purpose or by any other person or entity and may not be made available to
any other person or entity without our prior written consent.

                                        Sincerely,

                                        /s/ Cassels Brock & Blackwell LLP
                                        CASSELS BROCK & BLACKWELL LLP