POWER OF ATTORNEY

      The undersigned constitutes and appoints Joel Rubinstein, Daniel Nussen,
Zidong Liu, and Rana Ozer or any of them acting singly, as the undersigned's
true and lawful attorneys-in- fact and agents, with full power of substitution
and resubstitution, for the undersigned and in the undersigned's name, place and
stead, to:

      1.   prepare, sign, and submit to the Securities and Exchange Commission
(the "SEC") on its Electronic Data Gathering, Analysis, and Retrieval Filer
Management website a Form ID application, including any amendments and exhibits
thereto, and any other related documents as may be necessary or appropriate, to
obtain from the SEC access codes to permit filing on the SEC's EDGAR system,
granting unto said attorneys-in-fact and agents, and each of them, full power
and authority to do and perform each act and thing requisite and necessary to be
done as required by any rule or regulation of the SEC and the EDGAR Filer Manual
as fully and to all intents and purposes as the undersigned might or could do in
person, hereby ratifying and confirming all that said attorneys-in-fact and
agents, and each of them, may lawfully do or cause to be done by virtue hereof;
and

      2.   sign any and all SEC statements of beneficial ownership of securities
of Zanite Acquisition Corp. on Schedule 13D as required under Section 13 and
Forms 3, 4 and 5 as required under Section 16(a) of the Securities Exchange Act
of 1934, as amended, and any amendments thereto, and to file the same with all
exhibits thereto, and other documents in connection therewith, with the SEC, the
Company and any stock exchange on which any of the Company's securities are
listed, granting unto said attorneys-in-fact and agents, and each of them, full
power and authority to do and perform each act and thing requisite and necessary
to be done under said Section 13 and Section 16(a), as fully and to all intents
and purposes as the undersigned might or could do in person, hereby ratifying
and confirming all that said attorneys- in-fact and agents, and each of them,
may lawfully do or cause to be done by virtue hereof.

      A copy of this power of attorney shall be filed with the SEC.  The
authorization set forth above shall continue in full force and effect until the
undersigned revokes such authorization by written instructions to the attorneys-
in-fact.

      The authority granted hereby shall in no event be deemed to impose or
create any duty on behalf of the attorneys-in-fact with respect to the
undersigned's obligations to file a Form ID, Schedule 13Ds and Forms 3, 4 and 5
with the SEC.


Dated: September 14, 2021


                                        /s/ Patrick M. Shanahan
                                        -----------------------
                                        Patrick M. Shanahan