airports[c("name", "type")]

## class       : SpatialPointsDataFrame 
## features    : 2 
## extent      : 8.785862, 10.00565, 53.05229, 53.632  (xmin, xmax, ymin, ymax)
## coord. ref. : +proj=longlat +datum=WGS84 +no_defs +ellps=WGS84 +towgs84=0,0,0 
## variables   : 2
## names       :    name,  type 
## min values  :  Bremen, major 
## max values  : Hamburg, major

library(osrm)

route <- osrmRoute(airports[1, ], airports[2, ], sp = TRUE)

leaflet(width = "100%") %>% addProviderTiles("CartoDB") %>%
  addMarkers(data = airports, popup = ~ name) %>%
  addPolylines(data = route) %>%
  addControl(
    sprintf("<b>Duration</b>: %i min",
            as.integer(route$duration))
  )