You may meet the following enemy air forces during your
missions:
Helicopters
Helicopters are very slow, and are usually armed with
radar-guided missiles. Heat-seeking missiles
cannot be used against them. They sometimes carry chaff, but are
never fitted with electronic counter measures (ECM).
Prop-driven planes
These
are slow in comparison to the Harrier and may be armed with machine
guns, cannon, rockets or bombs. Their exhaust is not hot enough for
heat-seeking missiles to be used against them. They sometimes carry
chaff but are never fitted with ECM.
Fighter Jets
These
travel at a speed comparable to the Harrier. They may carry
heat-seeking or radar-guided missiles, rockets or bombs. They are
always fitted with ECM, so radar-guided missiles are
useless against them, but they do have a hot jet exhaust, so
heat-seeking
missiles may be used. They sometimes carry flares.
Fast Attack Jets
These advanced jets are faster than the Harrier. They
carry heat-seeking or radar-guided missiles, and may have flares
and chaff. They are never fitted with ECM.
Helicopters are very slow, and are usually armed with
radar-guided missiles. 
These
are slow in comparison to the Harrier and may be armed with machine
guns, cannon, rockets or bombs. Their exhaust is not hot enough for
heat-seeking missiles to be used against them. They sometimes carry
chaff but are never fitted with ECM.
These
travel at a speed comparable to the Harrier. They may carry
heat-seeking or radar-guided missiles, rockets or bombs. They are
always fitted with ECM, so 
These advanced jets are faster than the Harrier. They
carry heat-seeking or radar-guided missiles, and may have flares
and chaff. They are never fitted with ECM.