Each year English Heritage undertake a programme of aerial reconnaissance covering the whole of England. The reconnaissance is undertaken by the two Aerial Survey teams based in the Swindon and York offices. The York office staff cover the northern counties (Cumbria, Northumberland, Durham, Tyne and Wear, Cleveland, North Yorkshire, East Riding of Yorkshire, West Yorkshire, South Yorkshire, Lancashire, Merseyside, Cheshire, Staffordshire, Derbyshire, Nottinghamshire and Lincolnshire). In the first quarter of the 1999-2000 flying year (01/04/99-30/06/99), poor weather conditions resulted in limited flying opportunities. Flights over Yorkshire, Nottinghamshire and Lincolnshire showed promising developing cropmarks, especially on the limestone and chalk areas, but also on the gravels in the Trent valley. The second quarter (01/07/99-30/09/99) was highly productive in eastern England with good ground conditions. Highlights of new sites discovered include and hillfort in Nottinghamshire, a prehistoric ritual structure at the source of the Gypsey Race on the Yorkshire Wolds, and serveral new Neolithis cong barrow/mortuary enclosures in Lincolnshire and Yorkshire.In the third quarter (01/10/99-31/12/99), there were a number of good flying days. Scheduled monument monitoring was undertaken in Derbyshire, particularly of mining sites. A variety of earthworks sites in North Yorkshire, Cumbria, Nottinghamshire and Lincolnshrire were also recorded. Photography of the Saltaire proposed World Heritage site was also undertaken.The majority of the flying in the fourth quarter (01/01/00-31/03/00) occurred in January. Stereo oblique photography of mining remains on Bonsall Moor, Derbyshire was undertaken for the Peak District National Park Authority. A flight in February took advantage of low spring tides to photograph remanents of Bronze Age forest in the Humber estuary and more of a fishtrap complex discovered off Cleethorpes in 1998. The last flight on 30th March was undertaken principally to photograph architectural targets, but in transit, many excellent cropmarks were seen on the Yorkshire Wolds and, unusually, in the area between Hull and Beverley, suggesting that the dry and mild conditions prevalent in March have had a profound effect on crop growth.