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<br />II <br />II <br />II <br />II <br />II <br />II <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />3.7 ATC Limitations <br />Seeding flights during both periods were somE~times <br />hampered by Air Traffic Control (A TC) limitations on position and <br />altitude. The Operational Period was less affected by A TC :restric- <br />tions because there were considerably less traffic conflicts during <br />the hours of darkness. <br />Although no attempt has been made to classify A TC <br />delays, the most frequent occurred during periods when storms were <br />coming from the west or northwest. On several occasions the seed- <br />ing aircraft attempted to reac h a target cloud while other airplanes <br />were being diverted around the same cells. Since the ATC system <br />is designed to accept IFR traffic on a "first come, first served basis", <br />few alternatives were available to the pilot with which to adjust the <br />seeding delivery plans. In one instance, the aircraft was unable to <br />depart from Georgetown on an IFR clearance because of eXCE!ption- <br />ally heavy traffic near Dover. When it was possible to get the IFR <br />clearance, it was too late; the storm had already passed out to sea. <br /> <br />33 <br />