The market is competitive, each airline has 3,000 planes in the air
each morning. If the government imposes a $20.00 per ticket security
service tax on all tickets, what would be the expected effects on the
number of flights and the price (tax included)of the tickets?

Please use a diagram to explain.

Hi douger!
What will happen in most cases is that the equilibrium number of
flights will fall, while the price of each ticket, with tax included
will rise.

Let's assume that the firm must pay for this tax to the government.
The effect of this is that the cost of selling each ticket rises by
$20 (because now the firm must not only pay for the flight costs, but
also for the tax). Since the supply curve, in a competitive market, is
equal to the marginal costs curve (which rises by $20), this will
cause the supply curve to shift up (i.e. to the left) by $20. As
supply falls and demand remains the same, the price per ticket will
rise while the number of tickets sold will fall. You can see a diagram
(and an explanation) in the following page:

Indirect tax - What happens to the market price?
http://www.bized.ac.uk/virtual/economy/policy/tools/vat/vatth1.htm

You can also find in this page a discussion of on whom falls the
burden of the tax (consumers vs firms) depending on the price
elasticity of supply and demand. Notice that even though we have
assumed that the firm pays the tax to the government, it's true that
some of the burden of the tax falls on consumers, since now the price
of buying a ticket is higher, although it will probably not be $20
higher.

Elastic or Inelastic Demand
http://www.bized.ac.uk/virtual/economy/policy/tools/vat/vatth3.htm


Google search strategy
tax effects shift supply
://www.google.com/search?hl=en&lr=&ie=UTF-8&oe=UTF-8&q=tax+effects+shift+supply&lr=&start=10&sa=N


I hope this helps! If you have any doubt regarding my answer, please
request a clarification before rating it.


Best wishes!
elmarto

Great answer, plenty of information and concise.