<p>Anomalous long distance reports of Automatic Identification System (AIS) shipping transmissions were received by a United States Coast Guard terrestrial monitoring network in the eastern United States and Puerto Rico. 6677 signals were identified from ships located over 1000-km from the ground stations between 13 and 14 July 2021, with almost no long-distance links received at night or at any time on 15 July. The cause appears to be sporadic-E layers identified by Digisonde and satellite radio occultation data. The density of these layers cannot be accurately determined, but might exceed 27 MHz, or 9x10<sup>12</sup> el. m<sup>3</sup>. AIS transmissions potentially provide an excellent means of identifying dense sporadic-E layers globally.</p>