Well if realism is what you're after then here's some stuff right from the manual on sniper training and operations regarding extractions:
**Each mission has its specific problems associated with evasion and escape. The plan must conform to these unique problems while exploiting individual abilities, training of sniper team members, and supporting air or boat crews. The following general rules apply to evasion and escape plans for sniper operations:
a. The purpose of the plan is to attempt to save the individual who can no longer complete the assigned mission.
b. When sniper teams are behind enemy lines, the most successful escapes may involve air or water movement away from enemy-held territory.
c. Evasion and escape plans involve the following three phases:
(1) Phase one occurs during entry into the target area.
(2) Phase two occurs near the target area. It allows the sniper team to pursue its mission with a reasonable chance of success.
(3) Phase three occurs after the mission is accomplished. It is often the most difficult time to evade and escape.
d. The sniper team may be required to hide for several days to allow the enemy to become complacent before the team tries to move.
e. In selecting extraction sites, the sniper considers the danger of compromising other activities. He must prepare alternate plans for unforeseen developments.
AIR OR WATER EXTRACTION
Extraction by air or water is favored when resources are available and when it will not compromise the mission.
a. Other considerations that favor this method areas follows:
(1) Long distances must be covered.
(2) The time of return is essential.
(3) The enemy does not have air and naval superiority.
(4) Heavily populated hostile areas obstruct exfiltration.
(5) The team cannot be resupplied.
(6) Casualties must be extracted.
b. Several techniques maybe used to extract the team.
(1) Helicopter landing is the best method since the sniper team and its equipment can board the helicopter quickly.
(2) The troop ladder is the second best method. It lets sniper team members board the helicopter, but the helicopter can liftoff while snipers are still on the ladder.
(3) The STABO extraction system allows rapid pickup of one to four soldiers, who are suspended on lines beneath the helicopter. Soldiers are picked up and moved to an area where the helicopter can land. The sniper team then boards the helicopter.
(4) The jungle penetrator retrieves soldiers from areas where helicopters cannot land. It can pickup 1 to 3 persons at a time.
(5) The SPIES can extract soldiers from areas where helicopters cannot land. It can pickup 1 to 10 soldiers at a time.
6-14. LAND EXFILTRATION
This method is favored when snipers are not too far from friendly lines or no other means of extraction is available. It is also used when the terrain provides cover and concealment for foot movement and limits the employment of enemy mobile units against the exfiltrating team. Other considerations favoring this method are as follows:
a. Areas along exfiltration routes are uninhabited.
b. The enemy force is widely dispersed or is under such pressure that it is difficult for them to concentrate against the exfiltrating team.
c. The enemy force can stop an air or water extraction.
6-15. VEHICLE EXTRACTION
Vehicle extraction involves the exfiltration of the sniper team to an extraction site for extraction by a wheeled or tracked vehicle. Planning and coordination must be made during the preinsertion phase. Contingency plans must also be made to avoid compromise or any unforeseen situations.
Whew.... that was one long post.. but all usable
hope this helps